LU-14980 mdd: mdd_layout_swap() to follow tx-lock rule

LU-14980 mdd: mdd_layout_swap() to follow tx-lock rule

i.e. start transaction first, then take local (osd) locks
on the objects involved.

Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Change-Id: I9a4add277f0911fa02d9b214e996c441d0952f9c
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/44824
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Mikhail Pershin <mpershin@whamcloud.com>
Reviewed-by: Lai Siyao <lai.siyao@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>