owncloud/core

Bugfix: Do not mount shared storage which are failing

Some mounts use a shared storage, which points to a different storage.
If the underlying storage is removed, the share mount was still being
present as if the underlying storage could still be accessed. This was
causing problems with the `occ files:remove-storage --show-candidates`
command because the removed storage wasn't shown as possible candidate.

Now, that share storage won't be mounted, and the underlying storage
will be detected as a candidate to be removed with the command above.

https://github.com/owncloud/core/pull/41014