Comment 4 for bug 1779171

From an initial look this appears to be caused by this bit of code:

https://github.com/openstack/charm-rabbitmq-server/blob/master/hooks/rabbitmq_server_relations.py#L620

This change in behaviour was introduced by https://review.openstack.org/#/c/519594/ which looks like a mistake.

Work around is: juju config rabbitmq-server management_plugin=True