Goal: 

From RHOSO 19 onward, since Nova and Cinder are going to adopt the new
location API feature provided by Glance, we do not have to split by
default anymore, and we can provide a single Glance StatefulSet. This has
several advantages, and it simplifies several use cases (for example we can halve the PVCs resources required for staging area).
Due to updates/upgrade purposes, the split model must be kept to allow graceful transitions, which is not automatic, and a documented procedure will be provided. It is not possible to switch an existing GlanceAPI instance from "split" to "single" layout, and the operator does not automatically clean leftovers (e.g. existing PVCs, especially when Image cache is enabled). 

Acceptance Criteria:

It is possible to deploy a "single" GlanceAPI with a supported backend (s3, ceph, cinder, swift), for both a greenfield scenario and brownfield scenario.