worker: fix hang in VT_WAITACTIVE
    
    When plymouth deactivates it correctly leaves the display in
    GRAPHICS mode but incorrectly stops processing VT changes.  This
    combination of VT_AUTO + KD_GRAPHICS makes VT switches hang.
    
    Deal with the situation on our side until plymouth is fixed.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=745465