Don't run this scrub test if the kernel doesn't support scrub.
Fixes: f5f0c11a67a8f5 ("xfs: fuzz every field of every structure") Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Zorro Lang <zlang@kernel.org>