When using the glance v2 API the glance-registry service is
optional, and the intention is to remove the glance-registry
service in the S cycle.
The glance v1 API is scheduled to be removed in Queens.
This patch therefore disables the v1 API by default to give
us as much time as possible to identify the impact of that
and to get the issues resolved before it is removed from
the code-base.
The patch also cleans up the glance-registry init files
to handle the transition in an existing environment.
Tests are added to validate that enabling the v1 API still
works, and enabling the v2 registry still works.
Change-Id: I4c27aa0ca5b649e4fa76cfd0f326d80f50074db1
4fa9872510