LU-16915 tests: improve distro type checking

LU-16915 tests: improve distro type checking

Improve lustre_os_release() infrastructure to reduce redundant
code and make it easier to use.

Lustre-change: https://review.whamcloud.com/54790
Lustre-commit: 1ffbec13c0f745d0b9c6b91959b1afa52f99d63b

Test-Parameters: trivial
Fixes: 339b5e918f ("LU-16915 tests: except sanity-sec test_51")
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Id02223752df4eb3fd3b62b339e8c417eb33ebbe5
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/55213
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>