Run image size checks for newly-created events
    
    This enhances the consumer to run the image size
    check tests for newly-created validation events
    right after creating them. We needed to do this
    automatically somewhere, and this is as good a
    place as any. Only works if relval is available,
    but should fail gracefully if not.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>