dirmngr: Tell gpg about WKD lookups resulting from a cache.

* dirmngr/server.c (proc_wkd_get): Print new NOTE status
"wkd_cached_result".
* g10/call-dirmngr.c (ks_status_cb): Detect this and print a not ein
verbose mode.

This little patch is helpful to see why a WKD change still does not
work after it has been updated on the server.

• Signed-off-by: Werner Koch <wk@gnupg.org>