rtsp: fix StopBuffering condition in monitor

Stop buffering once there is sufficient data on all tracks.

Bug: 30230942
Change-Id: Iae484a4aab720c0bd70e0c122fd87e8237156019
(cherry picked from commit 91ea571836401ba77854d7b3aefb3ccee9c20eb3)
diff --git a/media/libmediaplayerservice/nuplayer/RTSPSource.cpp b/media/libmediaplayerservice/nuplayer/RTSPSource.cpp
index 8a305de..901f636 100644
--- a/media/libmediaplayerservice/nuplayer/RTSPSource.cpp
+++ b/media/libmediaplayerservice/nuplayer/RTSPSource.cpp
@@ -369,8 +369,11 @@
         startBufferingIfNecessary();
     }
 
-    if (overflow && mHandler != NULL) {
+    if (haveSufficientDataOnAllTracks()) {
         stopBufferingIfNecessary();
+    }
+
+    if (overflow && mHandler != NULL) {
         mHandler->pause();
     }