check_desktop: handle GNOME showing inactive button briefly
    
    check_desktop tries to catch when the overview is open and close
    it. But with GNOME 42, it seems the inactive "Activities" button
    is shown briefly on login before GNOME opens the overview. If
    check_desktop catches that, it will think the overview isn't
    open and it doesn't need to do anything. So if we match on first
    cycle through the loop, let's wait_still_screen then match again.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>