GlanceAPIs are based on StatefulSets. Given the nature of this k8s object, is not possible to update an existing API and plug/unplug PVCs.
However, the Glance operator exposes a `refreshGlanceAPI` function that can be used for this purpose, and it gives flexibility when a human operator would like to switch an API from PVCs to `storage.external: true` or vice versa, and optmize the way the staging area is consumed.

Improve the glance-operator to process the scenario described and allow it to rebuild the statefulset accordingly.