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 heard in IRC your comment about how "None" makes it API-available without making it part of the steps. I understand why you did this but can we put a comment here about why it's None.