xfs/620: force xattr leaf format for this test

xfs/620: force xattr leaf format for this test

Now that the kernel's parent pointer update code skips the attr intent
mechanism when the attr fork is in local/shortform format, we need to
bloat the attr fork to force the slow path for error injection testing.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Zorro Lang <zlang@kernel.org>