desktop_login: just reboot from console after user creation
    
    We don't *need* to log out from the desktop and reboot from the
    DM here, that's not part of the test (we test those features
    later using jim and jack). Now we don't black out the background
    of test's session in KDE, the logout needle doesn't match, so
    instead of redoing that needle all the time or re-adding the
    solidify_wallpaper call just to make one needle match reliable,
    let's just reboot from the console.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>