Update rabbitmq dependency

This commit updates the revision of rabbitmq to install for testing.

This revision was chosen for two reasons:

- later revisions remove the rabbitmq::server class
- later revisions do not support installing from your local distro (which
means you will likely get a version not tested with openstack)

Change-Id: Id73e7c9b43c25dbb6300c69565de2178b1a2462b