libstagefright: Add flush in reset during LPA playback

-If next operation is performed during LPA playback, delay is
observed before moving to next clip.
-Flush in reset happens only when playback is paused.
-Remove pause check to avoid delay and flush in cases where
next clip has been selected.

Change-Id: I561d83f70ef391f14bdb52bb8a6ee075e31e9531
CRs-Fixed: 395477