Remove force transition logic when keyguard is occluded.

This logic was introduced to fix the bug that calls couldn't be be picked
up when device is sleeping, but the problem is not reproducible anymore.

Bug: 182975035
Bug: 196355935
Test: Manual, and pass existing tests.
  1-1. Receive phone call while the screen is off.
  1-2. Check the phone activity responds to touch events.
  2-1. Set lock method (e.g. PIN or pattern)
  2-2. From the lockscreen, double tap power to launch camera.
  2-3. Take a photo.
  2-4. Tap a small preview photo image to launch the preview in full
       screen. Check no jarring during the transition.
Change-Id: I87f1b00e945f7cfd42d77d8f6621e951c23468d3