broadcasting a vp8 rtp stream from gstreamer

Just to confirm, @vpalmisano can you modify this line in mediasoup as follows?

- RTC::RTCP::FeedbackPsPliPacket packet(0, GetSsrc());
+ RTC::RTCP::FeedbackPsPliPacket packet(GetSsrc(), GetSsrc());

and see what happens? Even if it works, GStreamer is wrong about it.