Additonal changes:
* switch messaging related parameters to $::os_service_default
as they are used in oslo::messaging_rabbit define
* update unit tests
* update docs for notify::rabbitmq class
* drop deprecated rabbit_durable_queues parameter
* fix notification parameters according to mitaka config file
Change-Id: Ib20c13f136a299c958d9ac064e8ad93ceb0ebd40