Create a "wasListed()"-entry for API

DNSBL only shows active listed entries, but since we're only flagging entries as deleted to make them traceable, we may also publish information about IF the host has been blacklisted with us, to show at removal tool endpoint. This makes it possible to "victims" of blacklistings to confirm that their ip is removed, but have been listed before in case there is DNS services that still have the ip cached.