Prevent unexpected rotation while going back to keyguard

The original logic would let the app hidden by keyguard be able to
decide the orientation. While going back from a show-when-locked app
to keyguard, there would be a short time that keyguard is unable to
decide the orientation, which causes WMS uses the wrong orientation
from the wrong app.

https://code.google.com/p/android/issues/detail?id=155640

Change-Id: Ibc17bfe4603f68b241dc7380459ec9de42a3e259