Removes intefaces, moves cmd check to output and separate subsubtest from each other more precesely

This pull req

* Remove all interfaces from dockertest.
* Moves docker cmd check to output module
* Separate subsubtests from each other more precisely
I think I understand why this is disabled, but best put it in a comment so there is no question by anybody.  Catching all exceptions is needed in order to defer raising them until later, right?  How about stick this in the entire method's scope:

```python
# Catch-all exceptions here so they can be re-raised later, after all stages complete.
# pylint: disable=W0703
```