desktop_update_graphical: explicitly check refresh on GNOME
    
    OK, this is annoying. GNOME Software intentionally does *not*
    clear the 'download' or 'reboot and update' button when you hit
    the refresh button, it just leaves them sitting there while the
    refresh happens. So let's specifically require the 'refreshing'
    text to appear and go away before we try and click on download
    or apply.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>