ACodec: fix flush/resume for decoder-output-meta-data mode

When in decoder-output-meta-data mode, ACodec does not hold onto
buffers, but they are either with the native window, or with the
component/client.  However, for flushing we did not release the
discarded buffers back to native window (this makes sense because
they will be resubmitted shortly.)  This logic can be handled by
the normal resubmission.

Change-Id: Ic472b386422251515ef12f426e187f208f14decc
Signed-off-by: Lajos Molnar <lajos@google.com>
Bug: 10621959
Bug: 10192533