Add gnome-kiosk to critical-path-compose
    
    This is so we will run the everything-boot-iso openQA test on
    it, because the 'traditional' installer environment runs on
    gnome-kiosk, so we want to make sure gnome-kiosk updates are
    gated if they break the installer environment.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>