EX-9121 lipe: Trivial improvements for report merging

EX-9121 lipe: Trivial improvements for report merging

Small changes that do not affect the functionality, but allow to
reuse some functions in other parts of lipe3, for example in the
utility for merging different directory stats reports.

Test-Parameters: trivial testlist=sanity-lipe-scan3,sanity-lipe-find3
Signed-off-by: Vitaliy Kuznetsov <vkuznetsov@ddn.com>
Change-Id: Ib7eeeccb651e7bcff4ddfc78c66a35793df7bd1d
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/55232
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>