In order to allow definition of policies per service, we need to add variables
to 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: I594514580ca7180089699914805a595c2feb965b
e85299f413