After removing a volume, free_image tries to remove the parent
directory, so that no empty per-guest directories are left behind once
all images of a guest are gone. This was done unconditionally, so
deleting the last ISO, container template, snippet or import file also
removed the shared content directory like 'snippets' or 'template/iso'.
The directory gets re-created shortly after by pvestatd, but as
root:root with default permissions, losing any ownership or mode that
the admin set up, for example to allow a non-root user to upload
snippets.
Only clean up the parent directory for guest images, which are the only
volumes stored in per-guest directories.
Signed-off-by: Michal Fox <me@dualfroz.com>
