selinux-autorelabel: Use plymouth --quit rather then --hide-splash
    
    plymouth by defaults waits for 5 seconds before showing the splash so
    that the splash simply gets skipped on real quick boots.
    
    In my testing it seems that --hide-splash is a no-op when run before
    the 5 seconds have passed and the splash is shown, causing the splash
    to still be there during a relabel. Note this problem only shows when
    *not* using disk-encryption.
    
    Switching to plymouth --quit fixes this.
    
    Signed-off-by: Hans de Goede <hdegoede@redhat.com>