rtsp-client: changed session media iteration
rtsp-client: changed session media iteration

In client_unlink_session: now don't iterate in session->medias
list where items are removed by gst_rtsp_session_release_media.
Instead, repeatedly remove the first item.

surround-io/gst-rtsp-server,barisdemiray/gst-rtsp-server,thaytan/gst-rtsp-server,hsteinhaus/gst-rtsp-server,surround-io/gst-rtsp-server,Lachann/gst-rtsp-server,surround-io/gst-rtsp-server,hsteinhaus/gst-rtsp-server,barisdemiray/gst-rtsp-server,thaytan/gst-rtsp-server,Lachann/gst-rtsp-server,thaytan/gst-rtsp-server,Lachann/gst-rtsp-server,hsteinhaus/gst-rtsp-server,barisdemiray/gst-rtsp-server