Powerd : Stop on stopping ui, and start on x-started.
Powerd : Stop on stopping ui, and start on x-started.

This combination should avoid the X crashes on logout.
Also, this starts earlier too.

Change-Id: I5e18d087f4e0c503177dbf123f42cce2665a6875
Signed-off-by: Benson Leung <bleung@chromium.org>

BUG=chromium-os:5770
TEST=Boot system. Ensure that powerd starts using
initctl status powerd.
Ensure that backlight control works, and als works.

Review URL: http://codereview.chromium.org/3354021

joshfire/chromiumos-platform-init