GStreamer: disable clock syncing in video sink for live sources.

Task-number: QTBUG-38465
Change-Id: Icdf2df36b9b3c09dd047e60ac24e221a3d233c6f
Reviewed-by: Christian Stromme <christian.stromme@digia.com>

src/plugins/gstreamer/mediaplayer/qgstreamerplayersession.cpp

@@ -1535,6 +1535,7 @@ void QGstreamerPlayerSession::playbinNotifySource(GObject *o, GParamSpec *p, gpo
         qDebug() << "Current source is a non-live source";
 #endif
 
+    g_object_set(G_OBJECT(self->m_videoSink), "sync", !self->m_isLiveSource, NULL);
 
     gst_object_unref(source);
 }