pytest: fix flake in test_rbf_non_last_mined

A race condition seemed to be redirecting rpc before bitcoind processed
the second rbf transaction.

tests/test_opening.py

@@ -1320,7 +1320,7 @@ def test_rbf_non_last_mined(node_factory, bitcoind, chainparams):
     res = l1.rpc.fundchannel(l2.info['id'], chan_amount, feerate='7500perkw')
     chan_id = res['channel_id']
     vins = bitcoind.rpc.decoderawtransaction(res['tx'])['vin']
-    assert(only_one(vins))
+    assert only_one(vins)
     prev_utxos = ["{}:{}".format(vins[0]['txid'], vins[0]['vout'])]
 
     # Check that we're waiting for lockin
@@ -1358,8 +1358,13 @@ def censoring_sendrawtx(r):
 
     # Make a 3rd inflight that won't make it into the mempool
     signed_psbt = run_retry()
+    last = len(l1.daemon.logs)
     l1.rpc.openchannel_signed(chan_id, signed_psbt)
 
+    wait_for(lambda: l1.daemon.is_in_log("plugin-bcli: sendrawtx exit 0", start=last))
+    import time
+    time.sleep(.05)
+
     l1.daemon.rpcproxy.mock_rpc('sendrawtransaction', None)
     l2.daemon.rpcproxy.mock_rpc('sendrawtransaction', None)