Retry RabbitMQ connection and add vhost only if not present

Change-Id: Idb02d0d0f6405414e54b4f6526c0ed74c3c01de8
Reviewed-on: http://review.couchbase.org/36615
Reviewed-by: Tommie McAfee <tommie@couchbase.com>
Tested-by: Aruna Piravi <aruna@couchbase.com>