WIP: Shorten re-connect times on reloading the sidebar

This is a WIP for [this card](https://trello.com/c/cgeVlluY).

The intent is to avoid having a long response time from the server, if the client has just disconnected & reconnected, e.g. browser restart or reload of the sidebar.

The basic idea seems to work, but needs tidying & more extensive testing before this is ready to land.