ironic and cinder fail to run unit tests with master oslo.config

Trying to run unit test for Cinder or Ironic with the current oslo.config master branch result in a failure. Checking commits, the cause seems to be in https://review.openstack.org/537399 (a previous commit does not cause the issue), but I have not been able to find a cause.

The error message in Cinder unit tests is:

=========================
Failures during discovery
=========================
--- import errors ---
Failed to import test module: cinder.tests.unit.volume.drivers.test_zfssa
Traceback (most recent call last):
  File "/tmp/cinder/.tox/py27/lib/python2.7/site-packages/unittest2/loader.py", line 456, in _find_test_path
    module = self._get_module_from_name(name)
  File "/tmp/cinder/.tox/py27/lib/python2.7/site-packages/unittest2/loader.py", line 395, in _get_module_from_name
    __import__(name)
  File "cinder/tests/unit/volume/drivers/test_zfssa.py", line 38, in <module>
    from cinder.volume.drivers.zfssa import zfssanfs
  File "cinder/volume/drivers/zfssa/zfssanfs.py", line 76, in <module>
    CONF.register_opts(ZFSSA_OPTS, group=configuration.SHARED_CONF_GROUP)
  File "/tmp/cinder/.tox/py27/lib/python2.7/site-packages/oslo_config/cfg.py", line 2486, in __inner
    result = f(self, *args, **kwargs)
  File "/tmp/cinder/.tox/py27/lib/python2.7/site-packages/oslo_config/cfg.py", line 2684, in register_opts
    self.register_opt(opt, group, clear_cache=False)
  File "/tmp/cinder/.tox/py27/lib/python2.7/site-packages/oslo_config/cfg.py", line 2490, in __inner
    return f(self, *args, **kwargs)
  File "/tmp/cinder/.tox/py27/lib/python2.7/site-packages/oslo_config/cfg.py", line 2660, in register_opt
    return group._register_opt(opt, cli)
  File "/tmp/cinder/.tox/py27/lib/python2.7/site-packages/oslo_config/cfg.py", line 1887, in _register_opt
    if _is_opt_registered(self._opts, opt):
  File "/tmp/cinder/.tox/py27/lib/python2.7/site-packages/oslo_config/cfg.py", line 802, in _is_opt_registered
    raise DuplicateOptError(opt.name)
DuplicateOptError: duplicate option: zfssa_rest_timeout

In Ironic:

Captured traceback:
~~~~~~~~~~~~~~~~~~~
    Traceback (most recent call last):
      File "/usr/lib/python2.7/site-packages/mock/mock.py", line 1305, in patched
        return func(*args, **keywargs)
      File "/builddir/build/BUILD/ironic-10.2.0.dev84/ironic/tests/unit/common/test_utils.py", line 441, in test_check_dir_ok
        mock_exists.assert_called_once_with(CONF.tempdir)
      File "/usr/lib/python2.7/site-packages/mock/mock.py", line 318, in assert_called_once_with
        return mock.assert_called_once_with(*args, **kwargs)
      File "/usr/lib/python2.7/site-packages/mock/mock.py", line 947, in assert_called_once_with
        raise AssertionError(msg)
    AssertionError: Expected 'exists' to be called once. Called 61 times.