Allow quicker re-connect times when reloading the sidebar, or restarting the browser.

This is intended to fix potentially long re-connection times when reloading the sidebar or restarting the browser, as per [this card](https://trello.com/c/cgeVlluY).

The underlying issue is that when re-connecting within the 20 second long-polling timeout, the server doesn't really know the user has gone offline, and hence doesn't know to respond quickly.