db_mysql: fix ssl enforcing for mysql < 5.7

Completes 1e46a4b

Author: razvancrainea

modules/db_mysql/my_con.c

@@ -145,7 +145,9 @@ int db_mysql_connect(struct my_con* ptr)
 			(tls_opts & MY_CON_TLS_CIPHERS) ? ptr->tls_dom->ciphers_list:NULL);
 	}
 #if (defined LIBMARIADB) || (MYSQL_VERSION_ID < 80000)
+#if (MYSQL_VERSION_ID >= 50700)
 	mysql_options(ptr->con, MYSQL_OPT_SSL_ENFORCE, (void *)&use_tls);
+#endif
 #else
 	tls_opts = (use_tls?SSL_MODE_PREFERRED:SSL_MODE_DISABLED);
 	mysql_options(ptr->con, MYSQL_OPT_SSL_MODE, (void *)&tls_opts);