libstagefright: Fix to handle EAGAIN error on first read to source

 -Some of AV streaming clips are not played
 -In streaming use case when source does not have sufficent data it
  return error EAGAIN on first read request, player ignore this error
  and treat it as a first buffer.
 -Make the read request again to source on EAGAIN error.

Change-Id: I3feaccce757c17c4e80e6d62375c3d700ca29e72

media/libstagefright/AudioPlayer.cpp

@@ -110,7 +110,10 @@ status_t AudioPlayer::start(bool sourceAlreadyStarted) {
         mSeeking = false;
     }
 
-    mFirstBufferResult = mSource->read(&mFirstBuffer, &options);
+    do {
+        mFirstBufferResult = mSource->read(&mFirstBuffer, &options);
+    } while (mFirstBufferResult == -EAGAIN);
+
     if (mFirstBufferResult == INFO_FORMAT_CHANGED) {
         ALOGV("INFO_FORMAT_CHANGED!!!");