Add a wrapper around assert_and_click to handle signature change
    
    So, turns out new os-autoinst does *not* still accept the old
    argument style for assert_and_click...and old os-autoinst
    doesn't accept the new one. This adds a wrapper that handles
    both, so our tests can work with old and new os-autoinst. We can
    drop this once both deployments are on newer os-autoinst.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>