notify clients when publisher stopped broadcasting

[shaulfl]

trafficstars

In my use case I'm using ngnix-rtmp as rtmp proxy. When rtmp publisher disconnects, ffmpeg rtmp subscribers hangs indefinitely, and manually closing ffmpeg causes file corruption. This pull request resolves this issue by notifying client on publish/unpublish and handle it accordingly so ffmpeg exits gracefully.

[JasonRivers]

Thanks for this! However, in your PR you have disabled HLS, HLS is a large part of what's used on this image, Please could you remove disabling HLS and then I can merge this in.