LU-5100 llite: set dir LOV xattr length variable

the LOV xattr of directory could be either lov_user_md_v1
(size is 32) or lov_user_md_v3 (size is 48), then the actual
size of the LOV xattr should be return.

this patch also changes lod_verify_stripe to make it to accept
lov stripe from user and it's "pattern" is "LOV_PATTERN_RAID0".

Change-Id: I1ccba6da19aef0b7464c43b1b50871df44ce0eb7
Signed-off-by: Hongchao Zhang <hongchao.zhang@intel.com>
Reviewed-on: http://review.whamcloud.com/10453
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: jacques-Charles Lafoucriere <jacques-charles.lafoucriere@cea.fr>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>