Tempest test for vmware nsx certification fails

Issue

• Tempest failed to initialize on overcloud controller
• vmware_nsx certification test for tempest fails

2017-05-24 17:42:16.830 572706 ERROR tempest     on_load_failure_callback=self.failure_hook)
2017-05-24 17:42:16.830 572706 ERROR tempest   File "/usr/lib/python2.7/site-packages/stevedore/extension.py", line 93, in __init__
2017-05-24 17:42:16.830 572706 ERROR tempest     verify_requirements)
2017-05-24 17:42:16.830 572706 ERROR tempest   File "/usr/lib/python2.7/site-packages/stevedore/extension.py", line 171, in _load_plugins
2017-05-24 17:42:16.830 572706 ERROR tempest     self._on_load_failure_callback(self, ep, err)
2017-05-24 17:42:16.830 572706 ERROR tempest   File "/usr/share/openstack-tempest-13.0.0/tempest/test_discover/plugins.py", line 132, in failure_hook
2017-05-24 17:42:16.830 572706 ERROR tempest     raise err
2017-05-24 17:42:16.830 572706 ERROR tempest ImportError: No module named vmware_nsx_tempest.plugin
2017-05-24 17:42:16.830 572706 ERROR tempest