MyProxy: change private key cipher to EVP_aes_256_cbc()

As per #229 MyProxy still used an old cipher for encrypting private keys.
Changes courtesy of Mischa Salle (@msalle).

Fixes #229.

myproxy/source/ssl_utils.c

@@ -808,8 +808,7 @@ ssl_private_key_store_to_file(SSL_CREDENTIALS *creds,
     else
     {
         /* Encrypt with pass phrase */
-        /* XXX This is my best guess at a cipher */
-        cipher = EVP_des_ede3_cbc();
+        cipher = EVP_aes_256_cbc();
         pass_phrase_len = strlen(pass_phrase);
     }
 
@@ -1127,8 +1126,7 @@ ssl_proxy_to_pem(SSL_CREDENTIALS                *creds,
     else
     {
         /* Encrypt with pass phrase */
-        /* XXX This is my best guess at a cipher */
-        cipher = EVP_des_ede3_cbc();
+        cipher = EVP_aes_256_cbc();
         pass_phrase_len = strlen(pass_phrase);
     }