Description of problem:

Documentation here:

http://tripleo.org/advanced_deployment/root_device.html#using-introspection-data-to-find-the-root-device

indicates that wwn_vendor_extension is supported but when using this I get the following errors in ironic conductor logs:

2016-09-06 08:34:36.059 12275 ERROR ironic.drivers.modules.agent_base_vendor   File "/usr/lib/python2.7/site-packages/ironic/conductor/task_manager.py", line 
141, in wrapper
2016-09-06 08:34:36.059 12275 ERROR ironic.drivers.modules.agent_base_vendor     return f(*args, **kwargs)
2016-09-06 08:34:36.059 12275 ERROR ironic.drivers.modules.agent_base_vendor   File "/usr/lib/python2.7/site-packages/ironic/drivers/modules/iscsi_deploy.py",
 line 861, in continue_deploy
2016-09-06 08:34:36.059 12275 ERROR ironic.drivers.modules.agent_base_vendor     uuid_dict_returned = do_agent_iscsi_deploy(task, self._client)
2016-09-06 08:34:36.059 12275 ERROR ironic.drivers.modules.agent_base_vendor   File "/usr/lib/python2.7/site-packages/ironic/drivers/modules/iscsi_deploy.py",
 line 342, in do_agent_iscsi_deploy
2016-09-06 08:34:36.059 12275 ERROR ironic.drivers.modules.agent_base_vendor     raise exception.InstanceDeployFailure(reason=msg)
2016-09-06 08:34:36.059 12275 ERROR ironic.drivers.modules.agent_base_vendor InstanceDeployFailure: Failed to deploy instance: Failed to start the iSCSI targe
t to deploy the node b8e5dcac-ac83-4952-9e89-e11a36b41575. Error: {u'message': u'Error finding the disk or partition device to deploy the image onto: (\'No de
vice can be found because the following hints: "%(not_supported)s" are not supported by this version of IPA. Supported hints are: "%(supported)s"\', {\'suppor
ted\': \'model, wwn, vendor, serial, size\', \'not_supported\': \'wwn_vendor_extension\'})', u'code': 404, u'type': u'DeviceNotFound', u'details': [u'No devic
e can be found because the following hints: "%(not_supported)s" are not supported by this version of IPA. Supported hints are: "%(supported)s"', {u'supported'
: u'model, wwn, vendor, serial, size', u'not_supported': u'wwn_vendor_extension'}]}
2016-09-06 08:34:36.059 12275 ERROR ironic.drivers.modules.agent_base_vendor