Close users old games if they start a new online game

[Sothatsit]

Currently a user is able to close out of one game, and then join another. This causes issues because although the packets sent by the user will be forwarded to their active game, they are able to receive packets from all their existing games. Once a user starts a new game, it probably makes the most sense to just stop their old games.

This needs to be tested as well though to make sure that starting multiple games across multiple tabs should still be possible.