EX-9121 lipe: Add statistics merging for directories

EX-9121 lipe: Add statistics merging for directories

This patch adds the ability to merge statistics for directories.
This is the first of two patches and contains the basic collection of
information from json as well as basic output.

Test-Parameters: trivial testlist=sanity-lipe-scan3,sanity-lipe-find3
Signed-off-by: Vitaliy Kuznetsov <vkuznetsov@ddn.com>
Change-Id: I253f7606b66921eddf52709931cc1c880e66a997
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/55233
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alexandre Ioffe <aioffe@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>