Initialize RPC notification transport on starting magnum-api and
magnum-conductor. Here is the initialization sequence:
1. magnum.cmd.api.main()/magnum.cmd.conductor.main()
2. magnum.common.service.prepare_service()
3. magnum.common.config.parse_args()
4. magnum.common.rpc.init()
The last call setup a notifier that can be used to send notifications
via message queue.
Change-Id: Ibcc88d74a933d55ff33fad55e603786f9b4a3906
Partially-Implements: blueprint autoscale-bay
aeb401e5a5