Add support for webrtc helper

Change-Id: I0a7d9dca53b309ee24935a0c2232b8649247ba68
Send a webrtc BYE to fbstream on client disconnect

If the client socket just dies, there's no way for fbstream to find out
that this happened, so it keeps blasting away with video.

Change-Id: I27105ea5512244af820f11c993b8376ceba27000