EX-8191 lipe: Fix test for --collect-fsize-stats in lipe3

EX-8191 lipe: Fix test for --collect-fsize-stats in lipe3

This patch modifies the test for collecting statistics
in lipe3 and corrects:
1. Error getting a username if it doesnt already exist.
2. Error comparing file sizes after changing table
generation rules.
3. Converts the test from reading yaml to reading json
4. Now many files of different sizes are generated
for the test.
5. Now the data for comparison is retrieved from
the ls utility.
6. The test has added a check for creating a user with a
large UID, GID, which checks the availability of reports
for this user.

Test-Parameters: trivial testlist=sanity-lipe-scan3
Signed-off-by: Vitaliy Kuznetsov <vkuznetsov@ddn.com>
Change-Id: I7d0bdcc407bc0d27441c4204511dab2e6a421a5f
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/52424
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>