stream: set ttl-mc before adding the socket
stream: set ttl-mc before adding the socket

Set ttl-mc before adding the socket. Otherwise the value ttl-mc will
never be set on socket.

Fixes https://bugzilla.gnome.org/show_bug.cgi?id=724531

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