Skip CLI user tests because BZ #1144162

These tests was not failing, skipping them to make sure the BZ 1144162 does not make them fail. This action is needed to hopefully allow a green build.

Related to #1379

Thanks @Ichimonji10 to create the bugzilla.
Bugzilla bug 1144162 only affects UTF-8 characters. It is still possible to create a user with latin1, cjk, etc. characters. Thus, most of these tests should succeed. I handled the issue in `test_user_v2` like this:

```python
@data(
    {u'firstname', some_utf8_value, 'bugzilla': 1144162},
    {u'firstname', some_valid_value},
)
def test_something(self):
    bug_id = attrs.pop('bugzilla', None)
        if bug_id is not None and decorators.bz_bug_is_open(bug_id):
        self.skipTest('Bugzilla bug {0} is open.'.format(bug_id))
    # usual test code
```