dont trust the _NET_ACTIVE_WINDOW timestamp. (fixes bug #4519)
if we decide to focus the window, do not use their provided timestamp.
chromium gives a very old timestamp, which means we think we're focusing the
window but it never actually gets focus, leading to inconsistent behaviour by
openbox. use the timestamp for making decisions about passing focus if you
want (we dont right now), but not for the XSetInputFocus call.