It was writing out IPBlock CIDRs like "192.168.0.5/4" rather than
"192.0.0.0/4".
Also, simplify a bit by basing the `cidr` and the `except` both on
podB, rather than one on podA and one on podB. (This is even
theoretically a bugfix, since it's not _required_ that podA and podB
be in the same /4.) Also reorganize the code to make the two test
cases more consistent with each other.