dnsproxy: Prefer responses with ancount>0 if append_domain is true

If domain_append is true and a valid domain tld (eg. com. net. bz.)
is queried we need to make sure that responses with ancount>0 are
preferred over ones with ancount==0. This is due queries againts
valid domain tld's will always have response code ns_r_noerror even
there are no valid records. This will solve the issue dnsproxy not
returning the expected response if hostname queried is equal to any
valid tld.