LU-14975 dne: dir migration in non-recursive mode

LU-14975 dne: dir migration in non-recursive mode

Add an option "-d|--directory" option for "lfs migrate -m" to
migrate specified directory only, which is similar to "ls -d".

Add sanity 230w.

Lustre-change: https://review.whamcloud.com/44802
Lustre-commit: 5604a6d270b8be13a8aacd72a105fc72b5e16976

Signed-off-by: Lai Siyao <lai.siyao@whamcloud.com>
Change-Id: Ib97949e3840a3b49f7074b16e259582a9bf16e3b
Reviewed-on: https://review.whamcloud.com/45479
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Hongchao Zhang <hongchao@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>