RabbitMQ support

This adds a new parameter, amqp_server, which allows toggling between
rabbitmq and qpid as the amqp provider.  It also unifies the
configuration for both under a set of amqp_* parameters.  The former
qpid_* parameters have been renamed in this manner.
Update quickstack::pacemaker::nova to call new params in quickstack::nova.
Merge pull request #237 from jguiditta/rabbit_ha

Rabbit change to not break HA