Comment 0 for bug 1719268

Contrail blocks updating VNIC type [0], however it is a legal use case when using Ironic (baremetal provisioner) [1] due to several reasons:

1. With mixed clouds user may not know if instance will be placed on KVM or baremetal server.
2. Nova always create a ports with 'normal' vnic type, but even if it can pick vnic type dynamically we still need to update it for case when user pre-created a port (see case 1)

[0] https://github.com/Juniper/contrail-controller/blob/e3a0a81/src/config/api-server/vnc_cfg_types.py#L1303

[1] https://github.com/openstack/ironic/blob/b5863eb6b1e61092d42d05ae9e18918b598eb406/ironic/drivers/modules/network/common.py#L255