Ensure rabbitmq can be successfully restarted

We jump through many hoops in order to successfully restart rabbitmq.
This is mostly because we shift the rabbit PID file location, which
means that beam can't be correctly stopped.

Since we're installing static configuration, do that in the image
element rather than at runtime.

Then, ensure that rabbit isn't started until it's actually configured.

We do this in a fashion which is consistent with the operation of
os-svc-enable.

Change-Id: Ifee1dd90eb4db2c29a64864d1cc9fdc9cd3b1bfd
Merge "Ensure rabbitmq can be successfully restarted"