As mentioned in the Iced014acee7e590c10848e73feca166f48b622dc
commit message, in Ussuri+ we can use ``+sbwtdcpu none
+sbwtdio none`` as well. This is due to relying on RMQ-provided
erlang in version 23.x.

This change adds the extra arguments by default.
It should be backported down to Ussuri before we do a release with
Iced014acee7e590c10848e73feca166f48b622dc.

Change-Id: I32e247a6cb34d7f6763b544f247fd408dce2b3a2

Nova always tries to create the rabbitmq user regardless of
whether RabbitMQ is enabled or not.
This ps also adds an external rabbitmq doc.

Change-Id: Iec517226e4c82ea351889b55689a3efceaadcc76

On machines with many cores, we were seeing excessive CPU load on systems
that were not very busy. With the following Erlang VM argument we saw
RabbitMQ CPU usage drop from about 150% to around 20%, on a system with
40 hyperthreads.

    +S 2:2

By default RabbitMQ starts N schedulers where N is the number of CPU
cores, including hyper-threaded cores. This is fine when you assume all
your CPUs are dedicated to RabbitMQ. Its not a good idea in a typical
Kolla Ansible setup. Here we go for two scheduler threads.
More details can be found here:
https://www.rabbitmq.com/runtime.html#scheduling
and here:
https://erlang.org/doc/man/erl.html#emulator-flags

    +sbwt none

This stops busy waiting of the scheduler, for more details see:
https://www.rabbitmq.com/runtime.html#busy-waiting
Newer versions of rabbit may need additional flags:
"+sbwt none +sbwtdcpu none +sbwtdio none"
But this patch should be back portable to older versions of RabbitMQ
used in Train and Stein.

Note that information on this tuning was found by looking at data from:
rabbitmq-diagnostics runtime_thread_stats
More details on that can be found here:
https://www.rabbitmq.com/runtime.html#thread-stats

Related-Bug: #1846467

Change-Id: Iced014acee7e590c10848e73feca166f48b622dc

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