gpg: In search-keys return "Not found" instead of "No Data".
* g10/keyserver.c (keyserver_search): Check for NO_DATA.
(cherry picked from commit e7252ae57f3c9da557f23295268f74dd25fee3a1)
- GnuPG-bug-id: T3830
- Signed-off-by: Werner Koch <wk@gnupg.org>