Don't queue unnecessary discontinuity when switching tracks

NuPlayer originally would block on track switch until it receives a
discontinuity from each track (audio/video). This limitation has been
addressed in commit 53904f372b9c4a5ea7f839012b52b3d564e41207.

Bug: 23740080
Change-Id: I348f825ffba227904127b86c968b0acac9fd70d4
diff --git a/media/libmediaplayerservice/nuplayer/GenericSource.cpp b/media/libmediaplayerservice/nuplayer/GenericSource.cpp
index af2d0f3..0733113 100644
--- a/media/libmediaplayerservice/nuplayer/GenericSource.cpp
+++ b/media/libmediaplayerservice/nuplayer/GenericSource.cpp
@@ -666,7 +666,7 @@
               timeUs = mVideoLastDequeueTimeUs;
           }
           readBuffer(trackType, timeUs, &actualTimeUs, formatChange);
-          readBuffer(counterpartType, -1, NULL, formatChange);
+          readBuffer(counterpartType, -1, NULL, !formatChange);
           ALOGV("timeUs %lld actualTimeUs %lld", (long long)timeUs, (long long)actualTimeUs);
 
           break;