Switching server while loading causes glitchy behavior

[JamesKingdom]

Loading somewhere on the live server then switching to dev half way through causes the loaded data to remain and cause glitchy movement

[bhousel]

Good find @JamesKingdom - we have to cancel those async callbacks when the connection changes. 😢

[bhousel]

I added a bunch of code in 9b705a6 to avoid calling the OSM API callbacks after a connection reset or switch.

This mostly works, but there are still issues if you switch from "live" -> "dev" -> "live" very quickly.

This means there is still some state being stored somewhere and referenced from a deferred call. My suspicion is that this is in map.js. I think we need to add a proper Map.reset() method, to really throw out all the state and cancel all deferred work. But it's good enough for now.