Don't drop connections on ICE failure.

This spuriously breaks client-to-server connections over IPv6.
Thanks to Fabien de Montgolfier for his help with debugging this.

client.go

@@ -330,12 +330,6 @@ func addUpConn(c *client, id string) (*upConnection, error) {
 		sendICE(c, id, candidate)
 	})
 
-	pc.OnICEConnectionStateChange(func(state webrtc.ICEConnectionState) {
-		if state == webrtc.ICEConnectionStateFailed {
-			c.action(connectionFailedAction{id: id})
-		}
-	})
-
 	go rtcpUpSender(c, conn)
 
 	pc.OnTrack(func(remote *webrtc.Track, receiver *webrtc.RTPReceiver) {
@@ -664,12 +658,6 @@ func addDownConn(c *client, id string, remote *upConnection) (*downConnection, e
 		log.Printf("Got track on downstream connection")
 	})
 
-	pc.OnICEConnectionStateChange(func(state webrtc.ICEConnectionState) {
-		if state == webrtc.ICEConnectionStateFailed {
-			c.action(connectionFailedAction{id: id})
-		}
-	})
-
 	if c.down == nil {
 		c.down = make(map[string]*downConnection)
 	}