Active Keep-Alive connections are not closed before shutting down the loop

[Tragetaschen]

I'm currently tracking down ways the loop resource handle's Finalizer from #60 is called instead of the Dispose method.

One occurrence is when there are still active Connection: Keep-Alive connections that a browser could (and will) reuse. Those are still active handles on the loop and should be actively closed instead of implicitly through the shutdown logic.