This change adds support for encryption of communication between
OpenStack services and RabbitMQ. Server certificates are supported, but
currently client certificates are not.

The kolla-ansible certificates command has been updated to support
generating certificates for RabbitMQ for development and testing.

RabbitMQ TLS is enabled in the all-in-one source CI jobs, or when
The Zuul 'tls_enabled' variable is true.

Change-Id: I4f1d04150fb2b5af085b762890092f87ae6076b5
Implements: blueprint message-queue-ssl-support

Adds rabbitmq_server_additional_erl_args variable which
is appended to RABBITMQ_SERVER_ADDITIONAL_ERL_ARGS
environment variable to RabbitMQ server startup script.

This can be used to configure the schedulers.

Docs attached.

Change-Id: Id683c8cc6dac61354ffd94f3b460335b42136ba2
Co-authored-by: Radosław Piliszek <radoslaw.piliszek@gmail.com>
Related-bug: #1846467