LU-12324 mdd: Do not record xattr size get in changelogs

LU-12324 mdd: Do not record xattr size get in changelogs

It looks like if the xattr itself was not fetched there's no
need to create a changelog entry for it. The real get will come
and we'd do it there

Lustre-change: https://review.whamcloud.com/34936
Lustre-commit: 8f2599c599011a50549cdc79f0b3379239cf4f0c

Change-Id: I5b19f9309f65da0a4c58cb79a95787dab862eb94
Signed-off-by: Oleg Drokin <green@whamcloud.com>
Signed-off-by: Mikhail Pershin <mpershin@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Signed-off-by: Minh Diep <mdiep@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/35010
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>