Neutron-Ironic integration patch

Neutron-Ironic integration patch

This patch is in preparation for the integration
of Ironic and Neutron. A new vnic_type is being
added so that ML2 drivers can filter for all
Ironic ports based upon match for 'baremetal'.
Nova/Ironic will set this vnic_type when issuing
port-create request to neutron.
(e.g. binding:vnic_type = 'baremetal' )

Change-Id: I25dc9472b31db052719db503a10c1fb1a55572ef
Partial-Implements: blueprint neutron-ironic-integration