Stop forwarding port still forwards the port

[isidorn]

Refs: #85926

1. os x, open our express smoke test in a docker container with node10
2. npm install, open debug viewlet create a launch.json by clicking on the launch gear and press debug start
3. Forward a port 3000 to your localhost 3000. Hit the port locally and notice how you get the application
4. Stop Forwarding port 3000
5. Hit a port localy and notice that you still get the application even though you stopped the forwarding 🐛