[mediacodec] Return unprocessed input packets.

When a stream is stopped, return the unprocessed input packets to the
client who may be depending on that behavior.

TEST: fx shell set_root_view mediaplayer_test_util --test-seek /tmp/<files>
      fx shell set_root_view use_media_decoder --imagepipe --vp9 /tmp/<files>
Change-Id: I1c1aec546836f3875b0b68fbc92df57a20c1ab5f
2 files changed