MDEV-14429 sql_safe_updates in my.cnf not work

add a test case

mysql-test/include/mtr_warnings.sql

@@ -242,7 +242,7 @@ BEGIN
   DECLARE `pos` bigint unsigned;
 
   -- Don't write these queries to binlog
-  SET SQL_LOG_BIN=0;
+  SET SQL_LOG_BIN=0, SQL_SAFE_UPDATES=0;
 
   --
   -- Remove mark from lines that are suppressed by global suppressions

mysql-test/main/sql_safe_updates.opt

+--enable-sql-safe-updates

mysql-test/main/sql_safe_updates.result

+select @@sql_safe_updates;
+@@sql_safe_updates
+1

mysql-test/main/sql_safe_updates.test

+#
+# MDEV-14429 sql_safe_updates in my.cnf not work
+#
+select @@sql_safe_updates;