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.

CRs-Fixed: 569585
CRs-Fixed: 574967
Change-Id: Ia62f03e025310457df57e3106575fcc011e64a54