subtests.docker_cli: Add detach and interaction test

This pull request implements the https://github.com/autotest/autotest-docker/pull/192 inside the test instead of framework to give it time to stabilize before turning it into framework. I believe that this implementation is cleaner and easier to follow than hybrid implementation from https://github.com/autotest/autotest-docker/pull/194

Kind regards,
Lukáš
I like this class because it's under-stated and seems to just do the bare-minimum.  This is something we can grow on over time.  If it would help, it maybe doesn't even need to subclass ``AsyncDockerCmd``, it could just contain an instance.  Though it's fine either way.