pytest: fix flake in test_coinmoves_unilateral_htlc_timeout

We need to make sure anchor reaches bitcoind, otherwise it might mine
the commitment tx without it.  This can happen in
test_coinmoves_unilateral_htlc_fulfill as well.

```
>       check_chain_moves(l1, expected_chain1)

tests/test_coinmoves.py:844: 
...
E         Full diff:
E           [
E               {
E                   'account_id': 'wallet',
E                   'blockheight': 102,
E                   'created_index': 1,
E                   'credit_msat': 100000000000,
E                   'debit_msat': 0,
E                   'extra_tags': [],
E                   'output_msat': 100000000000,
E                   'primary_tag': 'deposit',
E                   'utxo': 'fca99b85e58f8ae23e5c6872e0500784997deb98bfc92e43449206553a108db2:1',
E               },
E               {
E                   'account_id': 'wallet',
E                   'blockheight': 103,
E                   'created_index': 2,
E                   'credit_msat': 0,
E                   'debit_msat': 100000000000,
E                   'extra_tags': [],
E                   'output_msat': 100000000000,
E                   'primary_tag': 'withdrawal',
E                   'spending_txid': 'c097ad8bde478396c961369b69c50a144fae3423f36af4554f3fb1dacfdff83f',
E                   'utxo': 'fca99b85e58f8ae23e5c6872e0500784997deb98bfc92e43449206553a108db2:1',
E               },
E               {
E                   'account_id': 'wallet',
E                   'blockheight': 103,
E                   'created_index': 3,
E                   'credit_msat': 25000000,
E                   'debit_msat': 0,
E                   'extra_tags': [],
E                   'output_msat': 25000000,
E                   'primary_tag': 'deposit',
E                   'utxo': 'c097ad8bde478396c961369b69c50a144fae3423f36af4554f3fb1dacfdff83f:1',
E               },
E               {
E                   'account_id': '3ff8dfcfdab13f4f55f46af32334ae4f140ac5699b3661c9968347de8bad97c0',
E                   'blockheight': 103,
E                   'created_index': 4,
E                   'credit_msat': 99970073000,
E                   'debit_msat': 0,
E                   'extra_tags': [
E                       'opener',
E                   ],
E                   'output_msat': 99970073000,
E                   'peer_id': '022d223620a359a47ff7f7ac447c85c46c923da53389221a0054c11c1e3ca31d59',
E                   'primary_tag': 'channel_open',
E                   'utxo': 'c097ad8bde478396c961369b69c50a144fae3423f36af4554f3fb1dacfdff83f:0',
E               },
E               {
E         -         'account_id': 'wallet',
E         +         'account_id': '3ff8dfcfdab13f4f55f46af32334ae4f140ac5699b3661c9968347de8bad97c0',
E                   'blockheight': 104,
E                   'created_index': 5,
E         -         'credit_msat': 0,
E         -         'debit_msat': 25000000,
E         -         'extra_tags': [],
E         -         'output_msat': 25000000,
E         -         'primary_tag': 'withdrawal',
E         -         'spending_txid': '1b6fbf9887d6f9cce727fc8bf9f582a3353be682998d4bafc9691c9ed26897e7',
E         -         'utxo': 'c097ad8bde478396c961369b69c50a144fae3423f36af4554f3fb1dacfdff83f:1',
E         -     },
E         -     {
E         -         'account_id': 'wallet',
E         -         'blockheight': 104,
E         -         'created_index': 6,
E         -         'credit_msat': Decimal('15579000.00000000'),
E         -         'debit_msat': 0,
E         -         'extra_tags': [],
E         -         'output_msat': Decimal('15579000.00000000'),
E         -         'primary_tag': 'deposit',
E         -         'utxo': '1b6fbf9887d6f9cce727fc8bf9f582a3353be682998d4bafc9691c9ed26897e7:0',
E         -     },
E         -     {
E         -         'account_id': '3ff8dfcfdab13f4f55f46af32334ae4f140ac5699b3661c9968347de8bad97c0',
E         -         'blockheight': 104,
E         -         'created_index': 7,
E                   'credit_msat': 0,
E                   'debit_msat': 49970073000,
E                   'extra_tags': [],
E                   'output_count': 5,
E                   'output_msat': 99970073000,
E                   'primary_tag': 'channel_close',
E                   'spending_txid': 'a499419bfdce179727cffca45429151db47839b247d83f71837429f021ae6322',
E                   'utxo': 'c097ad8bde478396c961369b69c50a144fae3423f36af4554f3fb1dacfdff83f:0',
E               },
E               {
E                   'account_id': 'external',
E                   'blockheight': 104,
E         -         'created_index': 8,
E         ?                          ^
E         +         'created_index': 6,
E         ?                          ^
E                   'credit_msat': 330000,
E                   'debit_msat': 0,
E                   'extra_tags': [],
E                   'originating_account': '3ff8dfcfdab13f4f55f46af32334ae4f140ac5699b3661c9968347de8bad97c0',
E                   'output_msat': 330000,
E                   'primary_tag': 'anchor',
E                   'utxo': 'a499419bfdce179727cffca45429151db47839b247d83f71837429f021ae6322:0',
E               },
E               {
E                   'account_id': 'external',
E                   'blockheight': 104,
E         -         'created_index': 9,
E         ?                          ^
E         +         'created_index': 7,
E         ?                          ^
E                   'credit_msat': 330000,
E                   'debit_msat': 0,
E                   'extra_tags': [],
E                   'originating_account': '3ff8dfcfdab13f4f55f46af32334ae4f140ac5699b3661c9968347de8bad97c0',
E                   'output_msat': 330000,
E                   'primary_tag': 'anchor',
E                   'utxo': 'a499419bfdce179727cffca45429151db47839b247d83f71837429f021ae6322:1',
E               },
E               {
E                   'account_id': 'external',
E                   'blockheight': 104,
E         -         'created_index': 10,
E         ?                          ^^
E         +         'created_index': 8,
E         ?                          ^
E                   'credit_msat': 50000000000,
E                   'debit_msat': 0,
E                   'extra_tags': [],
E                   'originating_account': '3ff8dfcfdab13f4f55f46af32334ae4f140ac5699b3661c9968347de8bad97c0',
E                   'output_msat': 50000000000,
E                   'primary_tag': 'to_them',
E                   'utxo': 'a499419bfdce179727cffca45429151db47839b247d83f71837429f021ae6322:4',
E               },
E           ]
```

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

tests/test_coinmoves.py

@@ -521,6 +521,7 @@ def test_coinmoves_unilateral_htlc_before_included(node_factory, bitcoind):
     check_chain_moves(l2, expected_chain2)
 
     close_info = l1.rpc.close(l2.info['id'], unilateraltimeout=1)
+    # Close, no anchor.
     bitcoind.generate_block(1, wait_for_mempool=1)
 
     # Make sure onchaind has digested it.
@@ -714,7 +715,8 @@ def test_coinmoves_unilateral_htlc_timeout(node_factory, bitcoind):
     line = l1.daemon.wait_for_log("Creating anchor spend for local commit tx ")
     anchor_spend_txid = re.search(r'Creating anchor spend for local commit tx ([0-9a-f]{64})', line).group(1)
 
-    bitcoind.generate_block(1, wait_for_mempool=1)
+    # Close, and anchor.
+    bitcoind.generate_block(1, wait_for_mempool=2)
     sync_blockheight(bitcoind, [l1, l2])
 
     # Make sure onchaind has digested it.
@@ -1024,6 +1026,7 @@ def test_coinmoves_unilateral_htlc_dust(node_factory, bitcoind):
     check_chain_moves(l2, expected_chain2)
 
     close_info = l1.rpc.close(l2.info['id'], unilateraltimeout=1)
+    # Close, no anchor.
     bitcoind.generate_block(1, wait_for_mempool=1)
     sync_blockheight(bitcoind, [l1, l2])
 
@@ -1217,7 +1220,8 @@ def test_coinmoves_unilateral_htlc_fulfill(node_factory, bitcoind):
     line = l1.daemon.wait_for_log("Creating anchor spend for local commit tx ")
     anchor_spend_txid = re.search(r'Creating anchor spend for local commit tx ([0-9a-f]{64})', line).group(1)
 
-    bitcoind.generate_block(1, wait_for_mempool=1)
+    # Close, and anchor.
+    bitcoind.generate_block(1, wait_for_mempool=2)
     sync_blockheight(bitcoind, [l1, l2])
 
     # Make sure onchaind has digested it.