unmount zfs rootfs

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
sys_pivot_root fixes

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
fs: Remove execute mode of files under fs directory

Signed-off-by: Asias He <asias@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>