This change implements and enables by default quorum support
for rabbitmq as well as providing default variables to globally tune
it's behaviour.
In order to ensure upgrade path and ability to switch back to HA queues
we change vhost names with removing leading `/`, as enabling quorum
requires to remove exchange which is tricky thing to do with running
services.
Change-Id: I4781a0c23274b145970b3269e517c2a62497acc4
c0783fcdf5