[Matrix]: more unit tests on get rows/cols.
[Matrix]: more unit tests on get rows/cols.

flashxio/FlashX,flashxio/FlashX,icoming/FlashGraph,icoming/FlashGraph,flashxio/FlashX,icoming/FlashX,flashxio/FlashX,icoming/FlashGraph,flashxio/FlashX,icoming/FlashX,icoming/FlashGraph,icoming/FlashX,flashxio/FlashX,icoming/FlashX,icoming/FlashGraph,icoming/FlashX