LU-10177 lfs: support DOM-to-OST migration

LU-10177 lfs: support DOM-to-OST migration

Migraton of DoM file to an OST file is possible with
'lfs migrate' command in general but would cause space loss
on MDS, because DOM local inode blocks are not deleted.
Patch doesn the following:
- adds truncate for local MDS inode after migration.
- check and prevent migration from non-DOM to DOM file,
  that will be done later with mirroring.
- prohibit 'lfs swap_layouts' command if either file has
  DOM component, 'lfs migrate' should be used instead

Signed-off-by: Mikhail Pershin <mpershin@whamcloud.com>
Change-Id: I1ce7b09eefab5e13f81af30c007475c927bd2874
Reviewed-on: https://review.whamcloud.com/32979
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>