Glance charm should stop deploying glance registry for v2 deployments at least as of Queens.
https://specs.openstack.org/openstack/glance-specs/specs/newton/approved/glance/deprecate-registry.html
"This spec proposes to deprecate the glance-registry service. Mark the service as deprecated and ready for removal in the Q release."
"With the release and support of Glance’s V2, the Glance Registry service has become redundant, hence this proposal to deprecate it."
https://blueprints.launchpad.net/glance/+spec/deprecate-registry
http://specs.openstack.org/openstack/glance-specs/specs/queens/approved/glance/deprecate-registry.html
"Glance deployments will eventually have to move away from using the registry. This can’t be done for glance-api nodes using v1 but it can certainly be done for v2-only nodes."
I think we still deploy with both API versions enabled, so we'll also need to disable the v1 api for the switch point where we stop deploying the registry service.