xfs: extended attribute fixes for CRCs

- Remove assert on count of remote attribute CRC headers
- Fix the number of blocks read in for remote attributes
- Zero remote attribute tails properly
- Fix mapping of remote attribute buffers to have correct length
- initialize temp leaf properly in xfs_attr3_leaf_unbalance, and
  xfs_attr3_leaf_compact
- Rework remote atttributes to have a header per block
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.10 (GNU/Linux)
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=VDbP
-----END PGP SIGNATURE-----