F I X  WIFISERVICE  W A R M   R E B O O T

WiFi open network notification: fix potential crash

set notification broadcast to null after unregistering it

Change-Id: I0645f54aadea9d86b69b365ba7e03d2d05d795be
Signed-off-by: Roman Birg <romanbirg@gmail.com>

Conflicts:

	services/java/com/android/server/WifiService.java