Comment 2 for bug 1642878

To elaborate on Satya's proposal, the messaging_interface & messaging_interface_address parameters could be added to Kolla and have a default value to that of the api_interface / address. The rabbitmq role template along with all other service role templates referring to rabbitmq address would need to be updated to replace api_interface_address messaging_interface_address.

We've tested these changes in our multinode / multirack dev environment.

Currently Kolla assumes that the primary hostname is set from the API interface. The changes proposed here could still allow for that assumption, while providing the option to override it.