test_controllers.sh script return value is always 0

[Cypresslin]

Even with issue #800 present, the controllers test won't be marked as failed because of the exit 0 in the end of the test_controllers.sh script.

This will make it harder to spot failures in this script. (Unless this is intended?)

[metan-ucw]

We are in the middle of cgroup tests rewrite, this script should be removed completely and new test should be written from scratch.

[metan-ucw]

@richiejp And this one. I suppose that we want to re-create the test coverage from scratch then delete these scripts.