CLI boundary tests

some more tests for issue #981
- subnet CRUD
- domain CRUD
I don't think it's a good idea to statically comment out test data. The problem is that, if BZ 1136088 is ever fixed, this test will still fail to run. Much better is to pass the data in, then skip during the test run itself if need be. You can use the `bz_bug_is_open` function to perform such a check. As an example of what I have in mind, see [this code](https://github.com/omaciel/robottelo/blob/master/tests/foreman/api/test_multiple_paths.py#L227-L228).