SPF::Mech: Do A/AAAA rather than ANY requests.

SPF::Mech#match_in_domain was doing ANY requests when looking for A/AAAA
results.  This will result in false-negatives when a DNS lookup of query
type TXT for example.com has already been done (and is cached by our
resolver) then an ANY query is done against the same cache.  In this
case the TXT record will be served from cache, while no address record
will be returned.

Instead, specifically send A and AAAA requests.