Fix assert_and_click call in realmd_join_cockpit
    
    This was just doing something silly before, but with recent
    os-autoinst having function signatures, it actually causes the
    test to fail because '5' isn't a sane value for the argument
    this was setting before. Fix it to set the timeout, as it was
    trying to do all along.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>