Quota storage wrapper is now used for all users in sharing mode

When accessing a shared folder, the folder's owner appears as mountpoint
but wasn't wrapped by a quota storage wrapper.

This fix makes sure that all home storages are wrapped by a quota
storage wrapper, if applicable, to make sure quotas are respected when
uploading into shared folders.
Now using the "Home" storage detection approach for quota

To find out whether to apply a quota, we now try and detect whether the
storage to wrap is a "Home" storage.