addresses parts of 3096779 and 3097475

3097475: Animation setting should control the screen on animation
3096779: CRT power-on animation can briefly show the top app instead of lockscreen

There is now a parameter that controls wether the ON and/or OFF animation are
performed. we also always clear the screen to black on power off, to make
sure it won't briefly appear on power on.
HOWEVER, 3096779 is not 100% fixed in the case where we're doing the animation
because there is a race, where SF doesn't wait (b/c it doesn't know) for the
framework to have redrawn the lockscreen.

Change-Id: Ie0f02c9225fcdf24b1e8907e268eb7da2c5b0a03