LU-4684 migrate: replace PFID via source

LU-4684 migrate: replace PFID via source

In directory migration, when it needs to update OST object PFID,
it should always do via source object, because target object may
be remote. And in this case, lod_obj_stripe_replace_parent_fid_cb()
doesn't compare parent FID with that in XATTR_NAME_FID, but set
with the passed in FID directly.

Signed-off-by: Lai Siyao <lai.siyao@whamcloud.com>
Change-Id: Icd7f6521ecac43cfeaee3e61e662d94115d63d68
Reviewed-on: https://review.whamcloud.com/33324
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>