Comment 5 for bug 1575229

So the goal with this bug is to denote that we shouldn't *need* to disallow IPv6. Probably we need to watch out for Dual Stack (both V4 and V6 at the same time would probably confuse us, but there isn't any reason to think that we couldn't handle v6 everywhere.)
Having GetAddressForInterface handle 4 or 6 would be the best, and getting rid of the "must not have v6" in the container networking code.