rtpstats: Base the packet rate average on the packet rate itself
rtpstats: Base the packet rate average on the packet rate itself

Do this so that the average update speed is in time instead of varying
based on the actual packet arrival rate.

pexip/gst-plugins-good,pexip/gst-plugins-good,GStreamer/gst-plugins-good,GStreamer/gst-plugins-good,GStreamer/gst-plugins-good,pexip/gst-plugins-good,pexip/gst-plugins-good,GStreamer/gst-plugins-good,pexip/gst-plugins-good