Cleanup Bitmap and buffer after setting up leash

- Recycle the Bitmap being used to draw the icon overlay for PiP right
  after setting the leash. This avoids Bitmap being leaked, eg. not
  recycled.
- Close also the hardware buffer to remove the reference to underlying
  buffer at the same time.

Flag: EXEMPT bugfix
Bug: 393584443
Test: manually, make sure the Bitmap is recycled and \
      no function regression
Change-Id: I46ec091432b235cb63ad7d40d73b39f3c1889470