During the ``kayobe overcloud inventory discover`` command, Kayobe
queries the Bifrost ironic node list and updates the Kayobe inventory.
If the nodes have a driver_info.ipmi_address field set, an ipmi_address
variable will be defined in the Kayobe inventory for the host.

This does not work for Redfish based hosts, which use
driver_info.redfish_address in the Ironic node. This change adds a new
``redfish_address`` variable and extends the command to discover the
address from the Bifrost node inventory.

Change-Id: Ieb1e61ddadb542732739d1f478b1e5a176e0ac88