webrtcbin: First keyframe is usually lost
The following discussion from !2260 (merged) should be addressed:
This pad probe is no longer necessary, libnice now drops all buffers before the stream is connected.
Does that mean we implicitly now depend on a particular libnice release, and if so which one?
Dropping packets at the start probably means we'll always lose bits of our initial keyframe for video. It might be good if we requested a keyframe automatically as soon as the connection is established.