LU-4684 lod: parse layout for migrating directory

LU-4684 lod: parse layout for migrating directory

If directory migration failed, it will be marked
LMV_HASH_FLAG_MIGRATION, lod_parse_dir_striping() should parse
layout for such directory, otherwise such directory can't be
accessed correctly.

Signed-off-by: Lai Siyao <lai.siyao@whamcloud.com>
Change-Id: I5ee2c2e3e5aa3f9befc3ad81be4bcdc6f9267842
Reviewed-on: https://review.whamcloud.com/33456
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Mike Pershin <mpershin@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>