Revert "BUG/MEDIUM: dns: fix long loops in additional records parse on name failure"

Revert "BUG/MEDIUM: dns: fix long loops in additional records parse on name failure"

This reverts commit fefce297ab5d0c36d6d6773092c976ea6166dc1e.

The commit broke the resolvers. All responses are marked as invalid. The
resolv_read_name() function can return 0 on error, but it seems also
possible to return 0 when no label name was found. And depending on the
caller, it can be an error... or not.

So, let's revert it. This might trigger a watchdog but doesn't seem to and
once fixed it makes things worse.

Must be backported as far as 2.4.