eventscheduler mismatch of my_{malloc,free}, delete

Fix malloc/delete mismatch. This causes a double free in the cleanup.

closes #1845

sql/event_scheduler.cc

@@ -436,7 +436,7 @@ Event_scheduler::start(int *err_no)
     scheduler_thd= NULL;
     deinit_event_thread(new_thd);
 
-    delete scheduler_param_value;
+    my_free(scheduler_param_value);
     ret= true;
   }