power: Stop X from turning our screen off

The default timeouts for DPMS in Xorg were finally applied after about
10 years:
http://cgit.freedesktop.org/xorg/xserver/commit/?id=6238bd68bd71323f8b4f1808f34dabe2ae447fe3

So work-around that horror.

https://bugzilla.gnome.org/show_bug.cgi?id=709114