Add names to the tests and use t.Run() (rather than having them just
be numbered, with number 9 mistakenly being used twice thus throwing
off all the later numbers...)
Remove unnecessary FakeNetwork element from the testCases struct since
it's always the same. Remove the expectedErr value since a non-nil
error is expected if and only if the returned set is nil, and there's
no reason to test the exact text of the error message.
Fix weird IPv6 subnet sizes.
Change the dual-stack tests to (a) actually have dual-stack interface
addrs, and (b) use a routable IPv6 address, not just localhost (given
that we never actually want to use IPv6 localhost for nodeports).
53b24f4ddf