Clarify task name
Clarify task name

Queue mirroring is an example of a policy that may be
applied by the task, but other policies, such as expiry
are also possible

Change-Id: I7496bbc2e983f64bc8ddcc91b9e6499641f4ba82

openstack/openstack-ansible-rabbitmq_server,openstack/openstack-ansible-rabbitmq_server