Handle new default job obsoletion behaviour in upstream openQA
    
    We used to obsolete existing pending jobs by default, and
    _ONLY_OBSOLETE_SAME_BUILD toned that down a bit. Now we don't
    obsolete existing pending jobs by default at all, and _ONLY_
    OBSOLETE_SAME_BUILD does nothing unless combined with _OBSOLETE,
    so let's just add _OBSOLETE to preserve the old behaviour as
    that's what we want.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>