Allow guest remote access to rabbitmq

Since RabbitMQ version 3.3.0, the guest user has no remote access,
document how to enable it for SUSE distros.

Backport: juno
Change-Id: I3032c8e867d3e367004907da8d8479dc61beca66
Closes-Bug: #1390419
(cherry picked from commit 69c9c65daeda311b7ccf28f8cce480e9fc63f723)