LU-9538 utils: fix lfs xattr.h header usage

LU-9538 utils: fix lfs xattr.h header usage

The lfs_getsom() code added the use of lgetxattr() to lfs.c, but
included the <attr/xattr.h> header instead of <sys/xattr.h> as
is used by other code in the tree.  That adds a dependency on
libattr-devel that we don't really need.

Test-Parameters: trivial
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I8cccccbdc7186d0ed1bfb1c12d911da763a44bf5
Reviewed-on: https://review.whamcloud.com/32918
Tested-by: Jenkins
Reviewed-by: Patrick Farrell <paf@cray.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Yingjin Qian <qian@ddn.com>
Reviewed-by: Quentin Bouget <quentin.bouget@cea.fr>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>