1. set fsc->mdsc after successfully allocate all necessary memory
in mdsc init.
2. if fsc->mdsc is NULL, just skip destroy operation in mdsc destroy.
Signed-off-by: NChengguang Xu <cgxu519@gmx.com>
Reviewed-by: N"Yan, Zheng" <zyan@redhat.com>
Signed-off-by: NIlya Dryomov <idryomov@gmail.com>