Lbaas tests can't be run alone by tox

When running 'tox -epy27 services.loadbalancer' the following failures are encountered:

Traceback (most recent call last):
  File "/home/eugene/quantum/neutron/tests/unit/services/loadbalancer/drivers/haproxy/test_agent.py", line 32, in setUp
    cfg.CONF.register_opts(agent.OPTS)
  File "/home/eugene/quantum/.tox/py27/local/lib/python2.7/site-packages/oslo/config/cfg.py", line 1540, in __inner
    result = f(self, *args, **kwargs)
  File "/home/eugene/quantum/.tox/py27/local/lib/python2.7/site-packages/oslo/config/cfg.py", line 1673, in register_opts
    self.register_opt(opt, group, clear_cache=False)
  File "/home/eugene/quantum/.tox/py27/local/lib/python2.7/site-packages/oslo/config/cfg.py", line 1544, in __inner
    return f(self, *args, **kwargs)
  File "/home/eugene/quantum/.tox/py27/local/lib/python2.7/site-packages/oslo/config/cfg.py", line 1662, in register_opt
    if _is_opt_registered(self._opts, opt):
  File "/home/eugene/quantum/.tox/py27/local/lib/python2.7/site-packages/oslo/config/cfg.py", line 486, in _is_opt_registered
    raise DuplicateOptError(opt.name)
DuplicateOptError: duplicate option: periodic_interval