Add verify_ports to agent verification

Listens for LLDP info on all interfaces, then attempts to match that to
the ports Ironic has, raising Verification errors if they don't match up.

Relies on https://review.openstack.org/#/c/92627/ for LLDP tools in the Agent.
I think `node_ports` is not very descriptive, when there are Ironic port objects in here too; can we use the word "switchports" in this name somewhere?