LU-17276 tests: Enqueue same range flocks

LU-17276 tests: Enqueue same range flocks

The ldlm_interval buffer will be released and referenced
between flocks or extent locks. Add a test case to trigger
such scene.

Signed-off-by: Yang Sheng <ys@whamcloud.com>
Change-Id: Ifa23ba7c16ad8601b1e3e7891a136589ea44e54a
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/53881
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>