When neutron is deployed with hypervisor is XenServer, current
implementation will grab port's iface-id via xapi, but this isn't
the proper way:
Port's iface-id is already set when creating VM or hot plugging
VIFs in nova project, so there is no need to grab it via xapi
Change-Id: Ie07527cc89ac81ff1e3519db66925cee482f77a4
Closes-Bug: #1649747