[Matrix]: fix bugs in unit test of mem vector vector.
[Matrix]: fix bugs in unit test of mem vector vector.

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