Add missing txn commit

Identified by @akildemir.

coordinator/tributary/tendermint/src/lib.rs

@@ -1068,6 +1068,7 @@ impl<N: Network + 'static> TendermintMachine<N> {
  let mut message_tape = txn.get(&message_tape_key).unwrap_or(vec![]);
  message_tape.extend(signed_msg.encode());
  txn.put(&message_tape_key, message_tape);
+ txn.commit();
  }
 
  // Re-broadcast this since it's an original consensus message worth handling