rec: Fix gathering of denial of existence proof for wildcard-expanded names

rec: Fix gathering of denial of existence proof for wildcard-expanded names

When the recursor is forwarding to a resolver, we accept the names composing
the CNAME chain starting at the queried name. This means we also need to gather
the denial of existence proof for CNAMEs that were expanded from a wildcard,
otherwise the response sent to the client cannot be DNSSEC-validated.