Check container interfaces in network

[Silcet]

As a workaround for the issue, I'm checking the interfaces of one container, then the interfaces of the docker network, and finally matching them.

[lukaszlach]

This is a nice and quality piece of code, thank you! The only concern I have is about the docker exec part requiring the container to have sh, cat and /sys present inside, which does not allow docker-tc to work with FROM scratch containers. Do you have any thoughts about this one?