libstagefright: Fix for LPA crash and timestamp issue

-Timestamps during LPA playback is incorrect.
Crash is observed during moving to next clip.
-Timestamp after seek is incorrect.
AudioFlinger does not call stop of LPA Audio session.
-Manage timestamps in LPAPlayer.
Call stop of LPA Audio session.

CRs-Fixed: 388808

(cherry picked from commit e839365b783893c8070da587dac8aa5cb56d63f4)

Change-Id: Icccfb7d2325beb0f19d85af67a6719171e3fa625