desktop_printing: wait a bit after switching back from console
    
    This test is failing a lot recently on KDE because when we try
    to launch konsole immediately after returning from a console to
    the desktop, it is mistyped and we get a browser instead. Let's
    try a little sleep after the switch back in case KDE just needs
    to settle down a bit.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>