Murano HA mode

Fix Murano HA mode:
* oslo.messaging used for murano-api and for 'system' RabbitMQ
* rabbit_hosts / rabbit_ha_queues are used
* haproxy added

Change-Id: I524179f76bc45525c4b9d4de75b655b5f8c52eed
Merge "Murano HA mode"