Work around Chromium bug of iceConnectionState stuck as "disconnected"

Due to a bug in Chromium the "iceConnectionState" of a RTCPeerConnection
may get stuck as "disconnected" even if the connection has already
failed. However, in that case "connectionState" does change to "failed",
so now its listened too to changes in "connectionState" to handle that
case.

Signed-off-by: Daniel Calviño Sánchez <danxuliu@gmail.com>