LU-15219 lfs: migration to DoM layout fix

LU-15219 lfs: migration to DoM layout fix

Migration to DoM layout from OST-striped file can skip
data sync beyond DoM component if it is not initialized.
Patch forces data copy prior layout merge, so new layout
is initialized and contains needed data

Tests 272e/272f in sanity.sh were modified to migrate data
for both MDT and OST parts

Fixes: 44a721b8c1 ("LU-11421 dom: manual OST-to-DOM migration via mirroring")
Signed-off-by: Mikhail Pershin <mpershin@whamcloud.com>
Change-Id: I206358e762780ab7cfaa7587888174a31bc7b196
Reviewed-on: https://review.whamcloud.com/45549
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>