Added rabbit clustering

Sets up rabbit clustering using the config file.
Having to do this is really eye-gougingly painful. Unfortunately, I have no idea what's rabbitmq's problem and why it leaves processes running. Worse still, this killall doesn't work reliably for me. Apparently, as killall kills one process, the killed process gets respawned by another process right before that process is killed as well. The result is that the `wait for rabbit to start` task never completes. I was able to stabilize this step by adding `with_sequence: count=2`