Fixes for proximity sensor behavior:

Add optional flag to Wakelock.release() to specify whether we should wait for proximity sensor to go negative before turning on the screen.
Clear the "waiting for proximity sensor to go negative" state when the power key is pressed.

Part of the fix for b/2243198 (Black screen lockup after ending call)

Change-Id: I813fdb7aa4192cd3384a25be9e59d7d4b90da53a
Signed-off-by: Mike Lockwood <lockwood@android.com>