Use a simple implementation for thread_safe_FIFO_queue.
Use a simple implementation for thread_safe_FIFO_queue.

The original implementation is tricky and has a concurrency bug.

silky/FlashGraph,flashxio/FlashX,silky/FlashGraph,zheng-da/FlashX,icoming/FlashX,zheng-da/FlashX,icoming/FlashX,icoming/FlashX,icoming/FlashX,icoming/FlashGraph,icoming/FlashGraph,zheng-da/FlashX,flashxio/FlashX,icoming/FlashGraph,icoming/FlashX,icoming/FlashGraph,silky/FlashGraph,flashxio/FlashX,silky/FlashGraph,flashxio/FlashX,silky/FlashGraph,flashxio/FlashX,icoming/FlashGraph,zheng-da/FlashX,flashxio/FlashX,zheng-da/FlashX