OpenStack uses 'CIDR' incorrectly in many places. We are not going
to perpetuate that usage. The correct name here is simply 'subnet'
as the data is the network address for the subnet, in CIDR notation.
Also, some additional cleanups as suggested in comments to
https://review.openstack.org/#/c/84782
Depends-on: I3c0748074a6511ff92500516b3129886d2476eed
Change-Id: Ib44c49dc1739ce7d881432e482dd16f8928eef49