fix a race condition of MediaPlayerServce::Client::mClient

there will be race condition between mClient.clear in MediaPlayerServce::Client::disconnect method
and c=client->mClient in in MediaPlayerServce::Client::notify method

Change-Id: I767294c4cb864c08e9c0e9f23d6d304a39016205
Signed-off-by: beanz <beanz@marvell.com>
diff --git a/media/libmediaplayerservice/MediaPlayerService.cpp b/media/libmediaplayerservice/MediaPlayerService.cpp
index c47fbd6..3a4122a 100644
--- a/media/libmediaplayerservice/MediaPlayerService.cpp
+++ b/media/libmediaplayerservice/MediaPlayerService.cpp
@@ -523,8 +523,8 @@
     {
         Mutex::Autolock l(mLock);
         p = mPlayer;
+        mClient.clear();
     }
-    mClient.clear();
 
     mPlayer.clear();