Camera3: only return input buffer when it is sent in request

This is to WAR the case where HAL sends non-NULL input_buffer in capture
result even capture framework doesn't send input buffer in the request.
It's very likely the input_buffer is uninitialized, and we shouldn't
use it. Log a warning for such case as well.

Bug: 16115675
Bug: 16117312
Change-Id: Ib299b45fbfe084059a9f546ded239c8094b039e2