PowerManagerService: Honor config_dreamsActivatedOnSleepByDefault

The current behavior causes isItBedTimeYetLocked to be called when
waking the device from a dream, which causes the display to blank.
On TV devices this is not the expected behavior.  Use the already
defined overlay config_dreamsActivatedOnSleepByDefault to skip the
call to isItBedTimeYetLocked and allow the screen to become active
again instead.  This will have not affect devices without the overlay.

Change-Id: I30c5c8c9c09e3d57ace18cac72b783510b9b3bf3