Clear unexpected buffer handle of sideband layer

If the buffer handle is not cleared after MediaCodec disconnected
and the surface is re-used for another sideband stream. SurfaceFlinger
would trigger incorrect composition type change from sideband to
device when SurfaceView layout changed.

Clear the buffer if the layer was about to set a new sideband
handle.

Bug: 291202822
Test: Adjust the screen layout after played 2 different sideband
stream. No composition type change.

Change-Id: I0b42d68ea03fb09db9aefc257d6071e559a3d8d2