As we can see from the previous test, l3 tells us why it rejected the payment:
```
lightningd-3 2024-11-19T03:56:27.151Z DEBUG 022d223620a359a47ff7f7ac447c85c46c923da53389221a0054c11c1e3ca31d59-chan#1: Failing HTLC because of an invalid payload (TLV 10 pos 104): cltv_expiry 136 > payment_constraint 130
```
It turns out, we were not updating the block height in the plugin!
Without this, when we create a (non-dummy) blinded path we set a
too-low CLTV restriction, and it doesn't work after a few blocks!
Note we were actually triggering this error in the xpay tests!
Reported-by: Vincenzo Palazzo
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Fixed: Offers: Receiving bolt12 payments where we have no public channels would fail a few blocks after startup.