LU-17923 lod: update layout ver for mirror merge/split

LU-17923 lod: update layout ver for mirror merge/split

In mirror extend/split, mdd_xattr_merge() and mdd_xattr_split() will
call mdd_object_pfid_replace() to update filter_fid for OST objects,
so we can update its layout version there.

This patch adds filter_fid::ff_layout_version in
lod_obj_stripe_replace_parent_fid_cb().

This patch adds ost_fid2_objpath() in test framework to derive OST
object path from its fid.

Signed-off-by: Bobi Jam <bobijam@whamcloud.com>
Change-Id: I68aca0e1f29c8e2800a28cfd3d630721ef869082
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/55388
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Mikhail Pershin <mpershin@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>