In order to allow definition of policies per service, we need to add variables
so service roles, that will be passed to openstack.osa.mq_setup.
Currently this can be handled by leveraging group_vars and overriding `oslomsg_rpc_policies` as a whole, but it's not obvious and
can be non-trivial for some groups which are co-locating multiple services
or in case of metal deployments.
Change-Id: I9faab7b89cc870a3580c622d3a9bab79c7500e8e
29bf7db198