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
Text-book advice:  When you have a class with only a constructor and one other function, you probably don't need a class.  Use a function or a lambda instead - MIght expand in future is an excuse, not a reason.