xfs_repair: ignore empty xattr leaf blocks

xfs_repair: ignore empty xattr leaf blocks

As detailed in the commit:

5e572d1a xfs: empty xattr leaf header blocks are not corruption

empty xattr leaf blocks can be the benign byproduct of the system
going down during the multi-step process of adding a large xattr
to a file that has no xattrs.  If we find one at attr fork offset 0,
we should clear it, but this isn't a corruption.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>