media: don't leak destinations
media: don't leak destinations

Refactor and cleanup the destinations array when the stream is destroyed.

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