dns: query_type is always equal to reply_type

Evdns only passes to us resources of the type that we have
requested, all the rest is skipped, e.g.:

    https://github.com/libevent/libevent/blob/master/evdns.c#L1112

Therefore, there is no need to store query_type when we issue
the query, because it will be equal to reply_type.
dns: fix default server name and add more tests