node with multi-port have unexpected behavior

[Tan Lin]

Create a node with multiple ports.
Deployment create multiple config under pxelinux.cfg and update ports' opts to neutron dhcp opts. But neutron only generate opts for only one port.
Because neutron only create one port for one instance, which only has one mac address.
This is may caused by Nova.
So we should disable multiple ports or enable neutron have multiple ports with one instance smoothly.

[Dmitry Tantsur (divius)]

The root of the problem at least partially may be in Nova, as with several ports present Nova chooses a random one. https://review.openstack.org/#/c/143480/ may help mitigate the problem on Ironic side.

[Dmitry Tantsur (divius)]

Also "only update one to neutron dhcp opts." is incorrect, see: https://github.com/openstack/ironic/blob/master/ironic/dhcp/neutron.py#L164