Send ACKs to the connection waiting on the ACK not the acker itself

- These ACKs are used to verify that commands published to the
  bus have been received and processed (e.g. group commands).
- Previously, ACKs only succeeded if the waiter and acker were on
  the same machine and/or the acker happened to be the waiter.

#3037
Something about the word `acker` cracks me up :laughing: