rtsp-media-factory-uri: don't autoplug parsers in a loop
rtsp-media-factory-uri: don't autoplug parsers in a loop

Stop autoplugging parsers if caps have parsed=true set. Fixes autoplugging
h264parse forever.

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