Teach ctld about CTL's physical_port and virtual_port fields.

This allows ctld to work with isp(4) virtual ports, specifying them as
isp0/1, isp0/2, etc. There are still problems on isp(4) layer with
disabling those ports after enabling, but hopefully they can be fixed.

MFC after: 3 days
Sponsored by: iXsystems, Inc.