rtsp-client: Fix iteration
rtsp-client: Fix iteration

Wouldn't even enter the code block otherwise (i++ was used as the check
and not the postfix).

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