lib/zonecut.c fetch_addr(): resurrect filtering by NO_IPV*
This filtering was dropped in 4565cc59 (v5.3.0). Now it's reintroduced - but inside the function, as that seems nicer.
As the code is designed so far (whole history probably), in order to detect whether we need to choose a zone cut closer to the root, we need to do this filtering in lib/zonecut.c already instead of just during server selection.
I don't think this change can break anything. Fetching unusable addresses from cache seems pointless, as selection wouldn't be allowed to use them or try resolving them.
Fixes #880 (closed)