[SAFS]: use original notify_completion in node_cached_io.
[SAFS]: use original notify_completion in node_cached_io.

global_cached_io has evolved significantly. I need to think of how to
optimize part_global_cached_io again.

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