Make sure plugin has got message to connectd before sending!
```
def test_even_sendcustommsg(node_factory):
l1, l2 = node_factory.get_nodes(2, opts={'log-level': 'io',
'allow_warning': True})
l1.connect(l2)
# Even-numbered message
msg = hex(43690)[2:] + ('ff' * 30) + 'bb'
# l2 will hang up when it gets this.
l1.rpc.sendcustommsg(l2.info['id'], msg)
l2.daemon.wait_for_log(r'\[IN\] {}'.format(msg))
l1.daemon.wait_for_log('Invalid unknown even msg')
wait_for(lambda: l1.rpc.listpeers(l2.info['id'])['peers'] == [])
# Now with a plugin which allows it
l1.connect(l2)
l2.rpc.plugin_start(os.path.join(os.getcwd(), "tests/plugins/allow_even_msgs.py"))
l1.rpc.sendcustommsg(l2.info['id'], msg)
l2.daemon.wait_for_log(r'\[IN\] {}'.format(msg))
> l2.daemon.wait_for_log(r'allow_even_msgs.*Got message 43690')
tests/test_misc.py:3623:
...
> raise TimeoutError('Unable to find "{}" in logs.'.format(exs))
E TimeoutError: Unable to find "[re.compile('allow_even_msgs.*Got message 43690')]" in logs.
contrib/pyln-testing/pyln/testing/utils.py:327: TimeoutError
```
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
043c4ae5eb