Work around RHBZ #1606541 (on Rawhide, not updates)
    
    We kind of want to know if FreeIPA is working aside from this
    known bug, so let's treat it as a soft failure and work around
    it. But only for Rawhide, not for F27/F28 updates tests.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>