Stop sending game state if client leaves mid rejoin.

[nani]

Currently the host keeps sending the game state to the client even if the client leaves the game before the upload to the client is finished. It turns out that the process of uploading is quite taxing on the host (frame rate drops quite significantly in my case and make things even more unresponsive) and would be nice if at least the upload process was killed when this case happens as to alleviate the host CPU and whatnot.

Thanks.

[wraitii]

Interesting idea, not possible in time for A24.

[Stan]

Unlikely to get done for A26

[Freagarach]

Pushing back.