Add a property to avoid redirection to the rtsp-sdp:// url but instead embeds an
rtspsrc element inside sdpdemux as the session manager.
Based on patch by Marco Ballesio.
Fixes#630046
When we are dealing with multiast, create the udp src and sink elements pointing
to the multicast addresses. When we are doing unicast, receive data on the local
ports and don't send RTCP because we don't know where we have to send it.
Fixes#583188
