Post-push fix: BUG#27619165: MTR UTILITY TO CRASH SERVER AND GET STACK TRACE

Use 'const' in one place.

Author: Sven Sandberg

sql/sql_parse.cc

@@ -3282,7 +3282,7 @@ int mysql_execute_command(THD *thd, bool first_level) {
         Makes server crash when executing SET SESSION debug = 'd,crash_now';
         See mysql-test/include/dbug_crash[_all].inc
       */
-      bool force_server_crash_dbug = false;
+      const bool force_server_crash_dbug = false;
       DBUG_EXECUTE_IF("crash_now", DBUG_ASSERT(force_server_crash_dbug););
 #endif