Add support for latest puppetlabs-rabbitmq

This patch adds a new paramter to the rabbitmq class
that allows a user to specify the class name. This allows
selection of 'rabbitmq::server' - the old name, or 'rabbitmq' -
the new name changed during the recent rewrite of the
puppetlabs-rabbitmq module.

Change-Id: I58c65d9f0eaa48aee49899c8850482c08320b003
Merge "Add support for latest puppetlabs-rabbitmq"