realmd_join_cockpit: only hit tab twice for Cockpit 245+
    
    Since 232, there's been a bug where we need to hit tab three
    times to get into the first field in the "Join domain" dialog.
    In 245, it's down to two times, for some reason. So, handle
    that.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>