engine: Do not report errors if libica does not support EC key

In case EC key creation using libica fails (for whatever reason), and
the software fallback is used to perform the operation, do not report
the errors that have been put to the error stack by the failing attempt
to use libica.

Fixes: a462093

Signed-off-by: Ingo Franzki <ifranzki@linux.ibm.com>

Author: ifranzki

src/engine/ibmca_ec.c

@@ -337,7 +337,9 @@ int ibmca_ecdh_compute_key(unsigned char **pout, size_t *poutlen,
     }
 
     /* Create ICA_EC_KEY object for private key */
+    ERR_set_mark();
     ica_privkey = ibmca_ec_make_and_cache_ica_key((EC_KEY*)ecdh, &privlen);
+    ERR_pop_to_mark();
     if (ica_privkey == NULL) {
         /* This curve is not supported by libica. */
     #ifdef OLDER_OPENSSL
@@ -502,7 +504,9 @@ ECDSA_SIG *ibmca_ecdsa_sign_sig(const unsigned char *dgst, int dgst_len,
     }
 
     /* Create ICA_EC_KEY object */
+    ERR_set_mark();
     icakey = ibmca_ec_make_and_cache_ica_key(eckey, &privlen);
+    ERR_pop_to_mark();
     if (icakey == NULL) {
         /* This curve is not supported by libica. */
  #ifdef OLDER_OPENSSL
@@ -633,7 +637,9 @@ int ibmca_ecdsa_verify_sig(const unsigned char *dgst, int dgst_len,
     }
 
     /* Create ICA_EC_KEY object */
+    ERR_set_mark();
     icakey = ibmca_ec_make_and_cache_ica_key(eckey, &privlen);
+    ERR_pop_to_mark();
     if (icakey == NULL) {
         /* This curve is not supported by libica. */
  #ifdef OLDER_OPENSSL