gpg: Do not require a trustdb for decryption.

* g10/trustdb.c (init_trustdb): Add and implement arg NO_CREATE.
Change to return an error code.  Change all callers to to pass False
for NO_CREATE.
(tdb_get_ownertrust): New arg NO_CREATE.  Call init_trustdb to test
for a non-existing trustdb.  Change all callers to to pass False for
NO_CREATE.
(tdb_get_min_ownertrust): Ditto.
* g10/trust.c (get_ownertrust_with_min): Add arg NO_CREATE.  Call
init_trustdb for a quick check.
(get_ownertrust_info): Add arg NO_CREATE.
(get_ownertrust_string): Ditto.
* g10/gpgv.c (get_ownertrust_info): Adjust stub.
* g10/test-stubs.c (get_ownertrust_info): Ditto.
* g10/mainproc.c (list_node): Call get_ownertrust_info with NO_CREATE
set.
* g10/pubkey-enc.c (get_it): Ditto.
--

Fixes-commit: effa80e0b5

For details see mails on Feb 27 and 28 by dkg, gniibe, and Justus to
gnupg-devel 'test failure on git master with
decrypt-session-key.scm (and: continuous integration?)'

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

g10/pubkey-enc.c

@@ -404,8 +404,13 @@ get_it (PKT_pubkey_enc *enc, DEK *dek, PKT_public_key *sk, u32 *keyid)
         hexfingerprint (pk, pkhex, sizeof pkhex);
         hexfingerprint (mainpk, mainpkhex, sizeof mainpkhex);
 
+        /* Note that we do not want to create a trustdb just for
+         * getting the ownertrust: If there is no trustdb there can't
+         * be ulitmately trusted key anyway and thus the ownertrust
+         * value is irrelevant.  */
         write_status_printf (STATUS_DECRYPTION_KEY, "%s %s %c",
-                             pkhex, mainpkhex, get_ownertrust_info (mainpk));
+                             pkhex, mainpkhex,
+                             get_ownertrust_info (mainpk, 1));
 
       }