Use PVC for glance store if powerflex is the storage backend.

[jijisa]

Is your feature request related to a problem? Please describe.
When the storage backend is powerflex, Glance store is set to file
due to a "cinder as a glance store" bug in powerflex cinder driver
(https://bugs.launchpad.net/cinder/+bug/2068548).

So the images are saved in /var/lib/glance/images/ which is the local
filesystem.

I do not want to save the image files in the host local filesystem since
their sizes are usually big so it occupies a lot of space in host filesystem.

Describe the solution you'd like

Add PVC and mount it onto /var/lib/glance/images so the image files are saved
in the storage backend instead of in the host local filesystem.

It is a temporary fix.
As soon as the bug I mentioned is solved, we can go back to cinder for
the glance store.

[jijisa]

I changed powerflex glance store to pvc.

Then, glance-api should be running with 1 replica only.
The glance storage init job should be skipped since it tries to mount the pvc volume
and it is not necessary for pvc store.

Lastly, I removed the dependency on storage init job to glance-api.

This is the temporary fix. We will set back to cinder store as soon as the bug is fixed by Dell.

The commit b60f5cd on feature/powerflex/use-pvc-for-glance-store branch solved this issue.