Remove RabbitMQ ulimit override (#2829)
Remove RabbitMQ ulimit override (#2829)

There is no need to carry the `rabbitmq_ulimit` override since it
matches the upstream value in OpenStack-Ansible.

Upstream patches:

  https://review.openstack.org/#/q/8f32edae0902bb7173b44c71398673510bd5b6cc
jacobwagner/rpc-openstack,robb-romans/rpc-openstack,rcbops/rpc-openstack,hughsaunders/rpc-openstack,hughsaunders/rpc-openstack,robb-romans/rpc-openstack,cloudnull/rpc-openstack,BjoernT/rpc-openstack,jacobwagner/rpc-openstack,cloudnull/rpc-openstack,rcbops/rpc-openstack,BjoernT/rpc-openstack