Fixed: Streams information is not updated properly for RTSP streams.

Changes to QGstreamerPlayerSession:
Handle video-changed, audio-changed, and text-changed signals.
Call getStreamsInfo() to update streams information.

Change-Id: I8bfead3268771245635424b5f1debff624bbe038
Reviewed-by: Jonas Rabbe <jonas.rabbe@nokia.com>
Reviewed-by: Ling Hu <ling.hu@nokia.com>
Reviewed-by: Dmytro Poplavskiy <dmytro.poplavskiy@nokia.com>

src/plugins/gstreamer/mediaplayer/qgstreamerplayersession.h

@@ -179,6 +179,8 @@ private:
     static void handleMutedChange(GObject *o, GParamSpec *p, gpointer d);
     static void insertColorSpaceElement(GstElement *element, gpointer data);
     static void handleElementAdded(GstBin *bin, GstElement *element, QGstreamerPlayerSession *session);
+    static void handleStreamsChange(GstBin *bin, gpointer user_data);
+
     void processInvalidMedia(QMediaPlayer::Error errorCode, const QString& errorString);
 
     void removeVideoBufferProbe();