pytest: really fix flake in test_reconnect_signed

```
>       l1.rpc.fundchannel(l2.info['id'], CHANNEL_SIZE)

tests/test_connection.py:667:
...
>           raise RpcError(method, payload, resp['error'])
E           pyln.client.lightning.RpcError: RPC call failed: method: fundchannel, payload: {'id': '022d223620a359a47ff7f7ac447c85c46c923da53389221a0054c11c1e3ca31d59', 'amount': 50000, 'announce': True}, error: {'code': -1, 'message': 'Disconnected', 'data': {'id': '022d223620a359a47ff7f7ac447c85c46c923da53389221a0054c11c1e3ca31d59', 'method': 'openchannel_update'}}
```

What happens here is complicated.

1. dualopend never processes the WIRE_COMMITMENT_SIGNED message, meaning it doesn't consider it worth
   trying to reconnect.
2. Normally, on disconnect, we give subds time to process packets and then notice the disconnect.
3. But, if we can another connection, we terminate the (old) subds immediately.
4. When lightningd transitions the channel from DUALOPEND_OPEN_INIT to DUALOPEND_OPEN_COMMIT_READY,
   it tells connectd this peer is important.
5. Normally, this causes a reconnect one second after hangup.
6. However, if we've already disconnected, it makes connectd reconnect immediately.  This causes
   the test flake, if dualopend hasn't processed the message, and thus changed the state to
   DUALOPEND_OPEN_COMMITTED: we don't reconnect and instead fail the fundchannel() call.

Signed-off-by: Rusty Russell <[email protected]>

Author: rustyrussell

tests/test_connection.py

@@ -654,12 +654,13 @@ def test_disconnect_half_signed_v2(node_factory):
 @pytest.mark.openchannel('v2')
 def test_reconnect_signed(node_factory):
     # This will fail *after* both sides consider channel opening.
-    disconnects = ['<WIRE_FUNDING_SIGNED']
     if EXPERIMENTAL_DUAL_FUND:
-        disconnects = ['<WIRE_COMMITMENT_SIGNED']
-
-    l1 = node_factory.get_node(may_reconnect=True, disconnect=disconnects)
-    l2 = node_factory.get_node(may_reconnect=True)
+        # Definitely in DUALOPEND_OPEN_COMMITTED once it's trying to send this.
+        l1 = node_factory.get_node(may_reconnect=True)
+        l2 = node_factory.get_node(may_reconnect=True, disconnect=['-WIRE_TX_SIGNATURES'])
+    else:
+        l1 = node_factory.get_node(may_reconnect=True, disconnect=['<WIRE_FUNDING_SIGNED'])
+        l2 = node_factory.get_node(may_reconnect=True)
 
     l1.fundwallet(2000000)