This introduces oslo.messaging variables that define the RPC and
Notify transports for the OpenStack services. These parameters
replace the rabbitmq values and are used to generate the messaging
transport_url for the service. The association of the messaging
backend server to the oslo.messaging services will then be
transparent to the keystone service.
This patch:
* Add oslo.messaging variables for RPC and Notify to defaults
* Update transport_url generation
* Update examples
* Add oslo.messaging to inventory
* Add release note
Depends-On: If4326a6848d2d32af284fdbb94798eb0b03734d5
Depends-On: I2b09145b60116c029fc85477399c24f94974b61d
Change-Id: I8d5b09dd0cb905e0dee40e260efbfeff1da180ce