[fuelclient] gate jobs are failing with max depth recursion

[Sylwester Brzeczkowski]

Fuelclient tests are failing in gate jobs like here https://review.openstack.org/#/c/244633/ and here https://review.openstack.org/#/c/222613/

2015-11-16 15:26:20.213 | File "/usr/local/lib/python2.7/dist-packages/tox/config.py", line 913, in _replace_env
2015-11-16 15:26:20.213 | env_list = self.getdict('setenv')
2015-11-16 15:26:20.213 | File "/usr/local/lib/python2.7/dist-packages/tox/config.py", line 839, in getdict
2015-11-16 15:26:20.213 | s = self.getstring(name, None)
2015-11-16 15:26:20.213 | File "/usr/local/lib/python2.7/dist-packages/tox/config.py", line 893, in getstring
2015-11-16 15:26:20.213 | x = self._replace(x)
2015-11-16 15:26:20.213 | File "/usr/local/lib/python2.7/dist-packages/tox/config.py", line 993, in _replace
2015-11-16 15:26:20.214 | return RE_ITEM_REF.sub(self._replace_match, x)
2015-11-16 15:26:20.214 | File "/usr/local/lib/python2.7/dist-packages/tox/config.py", line 989, in _replace_match
2015-11-16 15:26:20.214 | return handler(match)
2015-11-16 15:26:20.214 | File "/usr/local/lib/python2.7/dist-packages/tox/config.py", line 962, in _replace_substitution
2015-11-16 15:26:20.214 | return str(val)
2015-11-16 15:26:20.214 | RuntimeError: maximum recursion depth exceeded

Happens also locally. Downgrading tox to 2.1 solved the problem