* dirmngr/dns-stuff.c (libdns_res_open): New.  Replace all libdns_init
and dns-res_open by a call to this func.
(libdns_res_submit): New wrapper.  Replace all dns_res_sumbit calls.
(libdns_res_wait): New function.
(resolve_name_libdns): Replace loop by libdns_res_wait.
(get_dns_cert_libdns): Ditto.
(getsrv_libdns): Ditto.