LU-16896 flr: resync should not change file size

LU-16896 flr: resync should not change file size

mirror resync could punch a hole reaching the end of file in a
mirror, which could change the file size when the mirror is referred.

This patch calls truncate after punch in this case to keep the file
size unchanged in the mirror.

Signed-off-by: Bobi Jam <bobijam@whamcloud.com>
Change-Id: Ia0fc1f220a32a60f3516c69e86867796ae5c35c7
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/51344
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Mikhail Pershin <mpershin@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>