fix Octavia oslo_messaging_rabbit settings

Use recommended oslo_messaging_rabbit settings for Octavia which are already set for other services. This results in the following behaviour:

• stop using randomized substrings for queue names
• use quorum queues instead of classic queues
• use durable exchanges
• use stream queues for the publish/subscribe pattern (multiple non competing consumers)

To migrate existing exchanges to durable ones, the script ./tools/recreate-exchanges.sh needs to be executed. Afterwards upgrading the Octavia AMQPServer to version 4.2 will be functional.

Closes #635 (closed)