webrtcbin: Peer closing connection cause libnice to report FAILED as ICE connection state
If the peer closes the connection, we get the close_notify via the DTLS connection just fine and mark that one as properly closed. However shortly afterwards libnice reports
FAILED as the ICE connection state because the selected candidate pair times out or its connection is closed.
This should probably not happen and we should somehow get information from libnice that it's actually just closed and there's nothing fundamentally wrong at this point.