daemon: warp pointer to convenient place at startup
    
    This makes sure we always start the greeter window in a consistent
    place, and it makes sure the pointer doesn't start up on top of
    the greeter window.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=644327
    (cherry picked from commit 90ab791544d676629800e80fcf7a28a628f94e94)