Add gnome-disk-utility-nautilus in the GNOME desktop group
    
    Nautilus extension has been split out to a subpackage,
    since gnome-disk-utility-2.91.6-4. This is to avoid pulling
    in unnecessary gnome dependencies from the admin-tools group.
    
    https://bugzilla.redhat.com/show_bug.cgi?id=678909
    
    Signed-off-by: Kevin Kofler <Kevin@tigcc.ticalc.org>