Using pxe_ipmitool for introspection in OSP13 results in 'bmc_address': None error

Issue

• ironic-inspector.log

2018-08-15 22:50:33.026 21394 DEBUG ironic_inspector.node_cache [req-4cce735f-275d-430a-bc91-c416cf5188a5 - - - - -] Empty value for attribute bmc_address find_node /usr/lib/python2.7/site-packages/ironic_inspector/node_cache.py:803
2018-08-15 22:50:33.032 21394 INFO ironic_inspector.utils [req-4cce735f-275d-430a-bc91-c416cf5188a5 - - - - -] Could not find a node for attributes {'bmc_address': None, 'mac': [u'24:8a:07:87:13:ef', u'24:8a:07:87:13:ee']}
Look up error: Could not find a node for attributes {'bmc_address': None, 'mac': [u'24:8a:07:87:13:ef', u'24:8a:07:87:13:ee']}
Look up error: Could not find a node for attributes {'bmc_address': None, 'mac': [u'24:8a:07:87:13:ef', u'24:8a:07:87:13:ee']} error_response /usr/lib/python2.7/site-packages/ironic_inspector/main.py:68
2018-08-15 23:05:00.278 21394 INFO ironic_inspector.introspect [-] [node: 6d975d8d-4009-4f05-95e7-9f03c40cc256 state starting] The following attributes will be used for look up: {u'bmc_address': [u'10.240.116.221']}
2018-08-15 23:05:05.280 21394 INFO ironic_inspector.introspect [-] [node: 5e35c4aa-f85d-4245-8c15-dbf2ea8b266a state starting] The following attributes will be used for look up: {u'bmc_address': [u'10.240.116.222']}