LU-12511 utils: Move utilies specific values out of Lustre UAPI headers

LU-12511 utils: Move utilies specific values out of Lustre UAPI headers

Use FS_IOC_FS[S|G]ETXATTR directly. Move several things in the
UAPI header lustre_user.h that is only needed by user land tools
to the proper places.

Change-Id: Ie7a33742c0aba478c365c5fa44315400b28d8193
Test-Parameters: trivial
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-on: https://review.whamcloud.com/38790
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Wang Shilong <wshilong@ddn.com>