Set local `storage.*` config keys when CephFS pool gets configured

Currently MicroCloud configures the `storage.backups_volume` and `storage.images_volume` config keys only in case `local` storage gets configured.

If a user decides to only configure `remote` storage, those config settings aren't populated. However if the user decides to also setup a CephFS pool, we could still set the config keys.

Trace the existing path that sets storage.backups_volume and storage.images_volume during local storage configuration, then compare it with the CephFS pool configuration path. Confirm the keys are populated when remote storage is configured alongside a CephFS pool, and remain unset when no applicable pool is configured.

Written by the indexing model from the issue text.