Pin rabbitmq to 3.5.5 for RPM platforms.  This version is the latest
and sparkly with lots of bug fixes.  Tested multi-node HA and everything
seems solid in comparison to the 3.3.z releases used previously.

backport: liberty

Change-Id: I53bf70175fd12ded132141aa499c73919a932cdf
Closes-Bug: #1503280