libstagefright: Drain input buffer on resume

- Buffers returned from codec in paused state are not drained. When
codec is resumed these buffers are not drained until the next flush,
and may cause timed out issue.
- Added change to drain input buffers for sw decoders when resuming.

Change-Id: Ida2ab1d5dc3a1910accdd6fb89548262a912d8e7
CRs-Fixed: 569585, 574967