Add codfw subnets (now: remove pmtpa IPv6 networks)

Please review and merge when doing subsequent Puppet work to integrate
the codfw network & subnets into Puppet. Besides this, DNS and obviously
router/switch configs, I haven't added these anywhere else yet.

PS5: rebased on top of Icc6fce508504c0
     now just removes IPv6 networks from pmtpa that had already
     been added to codfw

Change-Id: Id14c9e831f97e075c050c560fcc310e43def4569