LU-16459 tests: fix YAML verification function

LU-16459 tests: fix YAML verification function

YAML verification function is not correct in tests.
Fix it and change test case accordingly.

Fixes: bedb797c5d ("LU-16110 lprocfs: make job_stats and rename_stats valid YAML")
Signed-off-by: Lei Feng <flei@whamcloud.com>
Test-Parameters: trivial
Change-Id: I109e2294aea3d1bffa08e6d2c39a5911fa8ef7df
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/49584
Reviewed-by: Li Xi <lixi@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>