Change several RabbitMQ config settings
Change several RabbitMQ config settings

"rabbit_userid", "rabbit_password", "rabbit_host" are deprecated for removal.
This patch changes these options to "transport_url" in DEFAULT group.

Change-Id: I0c33a1f84103d07e371e11229276c8cecdc485c4
Related-Bug: #1451226

ArchiFleKs/magnum,openstack/magnum,ArchiFleKs/magnum,openstack/magnum