dirmngr: Do a DNS lookup even if it is missing from nsswitch.conf.
* dirmngr/dns-stuff.c (libdns_init): Do not print error message for a missing nsswitch.conf. Make sure that tehre is a DNS entry.
- GnuPG-bug-id: T2948
- Signed-off-by: Werner Koch <wk@gnupg.org>