libstagefright: Fix for seek before end of clip issue

- When the clip is seeked to just before the end of the clip,
  the control skips to next track instead of the remaining part
  of the clip being played.
- When the clip is seeked, in LPAPlayerALSA, fillBuffer() is
  called which sets mReachedEOS to true when the last buffer
  is reached. AwesomePlayer on the other hand calls
  onCheckAudioStatus() after seek complete which in turn
  checks if reachedEOS() returns true in LPAPlayerALSA and
  calls postStreamDoneEvent(). Currently, reachedEOS() returns
  mReachedEOS which is incorrect because there still are
  buffers to be written to the DSP.
- Before postAudioEOS() is called, mReachedOutputEOS is set to
  true and is returned by reachedEOS().

CRs-Fixed: 339602 359591
(cherry picked from commit fe2345716be459f38088df2af79b53b1acf71d36)

Change-Id: I1334c8b0ab1e1d6cc386cc770c73ddc50af25c2e