Enable nightmode (screensaver) persistence through screen off/on.

WindowManager layoutparams in setWakeLock() didn't allow screensaver to
stay on through screen on/off toggles, similar to the funcitonality in
4.1.1 desk clock. Also onPause() in ScreensaverActivity.java executed
finish(), which stopped the screensaver.

I commented out the finish(), and put the setWakeLock() method back to
what it was in the 4.1.1 desk clock.

Change-Id: Ieab3a027342e77132ddea1f0ee69d2cb3a8bd140
Signed-off-by: Joseph Stover <doduff@gmail.com>