Hack: Manually call the timeout callback for connections where the timeout somehow got cancelled

After looking in to why ghost users occured and the differences between normal users, I found that the connection's `_session.to_tref._idleTimeout` property was -1 for all ghost users while a normal timeout value for normal users.
Simply calling `_session.timeout_cb` on those connections killed those connections.
This timeout is the timeout that sockjs sets to wait for users to reconnect within that time to continue their session.
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Merge pull request #522 from kotarou3/ghostUserBugfix

Hack: Manually call the timeout callback for connections where the timeout somehow got cancelled