libavcenc: Correct placement of sync synchronize

In entropy thread, after a call to __sync_synchronize(), store buffer is
receiving new entries. This is causing entropy threads to go out of sync,
resulting in erroneous bitstreams. The following change corrects this.

Bug: 130554568
Test: run cts -m CtsVideoTestCases -t
      android.video.cts.VideoEncoderDecoderTest#testAvcGoog0Qual0720x480
      --skip-preconditions

Change-Id: I81a2343f0f80c1e899e60e92fb48bbd3da006eab
1 file changed