Ctrl-C still hangs when hosting web-server in some cases

[jleibs]

Not sure which OS/browser combinations this hits. For me if I launch with rerun --web-viewer, and then ctrl-c it doesn't exit until I refresh the chrome tab that's opened.

Looks like we're hitting some variant of:

• Graceful shutdown never finishes when there is opened connection hyperium/hyper#1885

[Wumpf]

reproed on Windows. Can't shutdown from python .\examples\python\arkitscenes\main.py --serve, refresh does not fix it for me

[Wumpf]

Above report for windows --serve is fixed in #1939 but this has nothing to do with with the way Jeremy reports starting the viewer which isn't from python