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.

Test-Parameters: trivial
Test-Parameters: testlist=sanity-sec env=ONLY=51,HONOR_EXCEPT=y serverdistro=el9.3
Test-Parameters: testlist=sanity env=ONLY=906,HONOR_EXCEPT=y serverdistro=el9.3
Fixes: b881bd1051 ("LU-16915 tests: except sanity-sec test_51")
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Id02223752df4eb3fd3b62b339e8c417eb33ebbe5
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/54790
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>