Description of problem:

neutron.tests.unit.extensions.test_expose_port_forwarding_in_fip.TestExtendFipPortForwardingExtension.test_create_port_forwarding_and_remove_subnets
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Captured traceback:
~~~~~~~~~~~~~~~~~~~
    Traceback (most recent call last):
      File "neutron/tests/base.py", line 181, in func
        return f(self, *args, **kwargs)
      File "neutron/tests/unit/extensions/test_expose_port_forwarding_in_fip.py", line 259, in test_create_port_forwarding_and_remove_subnets
        insub3['subnet']['id'], None)
      File "neutron/tests/unit/extensions/test_l3.py", line 422, in _router_interface_action
        self.assertEqual(expected_code, res.status_int, msg)
      File "/home/cloud-user/neutron/.tox/py27/lib/python2.7/site-packages/testtools/testcase.py", line 411, in assertEqual
        self.assertThat(observed, matcher, message)
      File "/home/cloud-user/neutron/.tox/py27/lib/python2.7/site-packages/testtools/testcase.py", line 498, in assertThat
        raise mismatch_error
    testtools.matchers._impl.MismatchError: 200 != 409
Version-Release number of selected component (if applicable):


How reproducible: 100%


Steps to Reproduce:
1. Clone neutron on RHEL 8 and run 'tox -e py27'