Do not try to focus upon _NET_WM_USER_TIME property change event
Do not try to focus upon _NET_WM_USER_TIME property change event

When this property is changed on a window and `follow_mouse_focus` is
False, that window is focussed by Qtile. However, this behaviour is not
described in the specification and causes unexpected side effects.
Fixes #2172

qtile/qtile,ramnes/qtile,qtile/qtile,ramnes/qtile