LU-3268 lod: return root LOV EA in little-endian

In lod_xattr_get() when constructing LOV EA to return for the
filesystem root, store members in little-endian byte order for
consistency with EAs from disk.

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: Id76da869e14ff71b8af21fe2b1d66abd54da0a2d
Reviewed-on: http://review.whamcloud.com/6285
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Li Wei <wei.g.li@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>