A new relation with primary/secondary nomenclature is added and the
old master/slave relation is marked as *Deprecated*. In future,
master/slave relation would be completely removed.
Change-Id: I9cda48b74a20aaa9a41baedc79332bfaf13951d3
func-test-pr: https://github.com/openstack-charmers/zaza-openstack-tests/pull/926