freertos: fix protection issue in freertos queue event list
When functions in queue.c calls listLIST_IS_EMPTY() to check queue event list, the queue list is
protected by queue mutex, on the other hand, when xTaskIncrementTick() modify the queue list, the
queue list is protected by xTaskQueueMutex, this may cause xTaskRemoveFromEventList operate on
the empty queue list and cause problem.
This change works around the problem by reducing the window where the race condition can happen.
See merge request !465
01c4a980ee