fix ssh tests when compiled w/o MPI provider

tests/ssh_test.c

@@ -294,6 +294,8 @@ static int _ssh_decoding_test(void)
 */
 int ssh_test(void)
 {
+   if (ltc_mp.name == NULL) return CRYPT_NOP;
+
    DO(_ssh_encoding_test());
    DO(_ssh_decoding_test());