Ensure "rabbit_use_ssl" is specified in the [oslo_messaging_rabbit]
config section instead of "ssl" for Ocata, since "ssl" was not yet
introduced.
This is fixed by using section-oslo-messaging-rabbit for pike and
above rather than ocata and above, and using section-rabbitmq-oslo
for ocata.
Change-Id: I9209a3cdc9b52a918621ad2c328e67aa616f18d6
Closes-Bug: #1838696