sm: Fix certificate creation with key on card.

* sm/certreqgen.c (create_request): Fix for certmode.
--

When using an existing key from a card for certificate signing (in
contrast to the default of generating a CSR), the code tried to use
the same key for signing instead of the Signing-Key parameter.  It is
perfectly okay to use the regular signing path via gpg-agent for
certificate creation - only self-signed certificates with a key on the
card require the direct use of the card key (via "SCD PKSIGN").

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

sm/certreqgen.c

@@ -1314,7 +1314,7 @@ create_request (ctrl_t ctrl,
           log_info ("about to sign the %s for key: &%s\n",
                     certmode? "certificate":"CSR", hexgrip);
 
-          if (carddirect)
+          if (carddirect && !certmode)
             rc = gpgsm_scd_pksign (ctrl, carddirect, NULL,
                                    gcry_md_read (md, mdalgo),
                                    gcry_md_get_algo_dlen (mdalgo),