When deploying on IPv6 stateful ironic must use the
neutron network interface driver. This because we need
to configure neutron service ports (provisioning, cleaning
etc.) with multiple ip addresses for certain UEFI firmware
and chainloading combinations (iPXE -> Ironic IPA) to work.
Closes-Bug: #1864491
Change-Id: I5a9890ccb95a21b95f488cd7a5b5fd1a6cdff38b