Comment 4 for bug 1823880

I agree with Sean, we shouldn't delete the cache when we delete the last volume associated.

In my opinion we should delete it when we request to delete the volume type, and cached volumes should not be taken into consideration at the API to determine if a volume type can be removed.

Solving this in Cinder may be somewhat complicated. Volume types don't have a status we can change while we try to delete the cached volume to prevent races, we cannot delete the type before the volume, and deleting the volume before the type could create race conditions where somebody else uses the type for a new volume and we can no longer delete the type...