Fix a playback bug for mediaplayer windows media foundation backend

Task-number:QTMOBILITY-1606

Reviewed-by:Jonas Rabbe
(cherry picked from commit d5426bf52e19c9c6a52837b423f48024979ea076)

Change-Id: Ie7c1c90a8f5a64e77c435ffc1917d8f9638dfff3
Reviewed-on: http://codereview.qt-project.org/5499
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Michael Goddard <michael.goddard@nokia.com>

src/plugins/wmf/player/mfplayercontrol.cpp

@@ -72,7 +72,12 @@ MFPlayerControl::~MFPlayerControl()
 
 void MFPlayerControl::setMedia(const QMediaContent &media, QIODevice *stream)
 {
-    stop();
+    if (m_state != QMediaPlayer::StoppedState) {
+        changeState(QMediaPlayer::StoppedState);
+        m_session->stop(true);
+        refreshState();
+    }
+
     m_media = media;
     m_stream = stream;
     resetAudioVideoAvailable();