MEDIUM: tasks: Use __ha_barrier_store after modifying global_tasks_mask.

Now that we no longer use atomic operations to update global_tasks_mask,
as it's always modified while holding the TASK_RQ_LOCK, we have to use
__ha_barrier_store() instead of __ha_barrier_atomic_store() to ensure
any modification of global_tasks_mask is seen before modifying
active_tasks_mask.

This should be backported to 1.9.

src/task.c

@@ -78,7 +78,7 @@ void __task_wakeup(struct task *t, struct eb_root *root)
 #ifdef USE_THREAD
 	if (root == &rqueue) {
 		global_tasks_mask |= t->thread_mask;
-		__ha_barrier_atomic_store();
+		__ha_barrier_store();
 	}
 #endif
 	_HA_ATOMIC_OR(&active_tasks_mask, t->thread_mask);