Handle rabbitmq cluster shortnames explicitly.

Rabbitmq can get confused if the hostname, which is used
for the erlang vm name, does not match the resolved name
for a host. This comes up in multi-homed environments
where /etc/hosts populated with the managament addresses, and
rabbit traffic should be going over a different interface.

Change-Id: I81f5af73c727d7eb3be7e4f91db42dcb25f099fb
Merge "Handle rabbitmq cluster shortnames explicitly."