Add back necessary tests for deprecated settings that are replaced during applying inclusive naming

[tlfeng]

Is your feature request related to a problem? Please describe.
Issue #2769 shows a fault caused by PR #2463 (Deprecate setting 'cluster.initial_master_nodes' and introduce the alternative setting 'cluster.initial_cluster_manager_nodes' ).
The backwards compatibility was broken by mistake.
In the above PR, the deprecated setting name is replaced directly by the new setting name in the existing tests, while new unit tests for validating backwards compatibility didn't cover all the cases.
The defect should be avoided.

Describe the solution you'd like

• Revise all the PRs about deprecated setting with non-inclusive term while adding new setting in Add alternative usages for the REST APIs and configurations that contain "master" terminology #1549:
  In detailed, they are:
  Add a new node role 'cluster_manager' as the alternative for 'master' role and deprecate 'master' role #2424
  Deprecate setting 'cluster.service.slow_master_task_logging_threshold' and introduce the alternative setting 'cluster.service.slow_cluster_manager_task_logging_threshold' #2451
  Deprecate setting 'cluster.no_master_block' and introduce the alternative setting 'cluster.no_cluster_manager_block' #2453
  Deprecate setting 'cluster.initial_master_nodes' and introduce the alternative setting 'cluster.initial_cluster_manager_nodes' #2463
• Add replaced tests back where the new unit tests didn't cover the case.

Describe alternatives you've considered
none.

Additional context
none.

[anasalkouz]

Are we going to duplicate the test to cover old and new usages? Can you create another issue to clean up those duplicate tests on 3.0?

[tlfeng]

@anasalkouz Yes. I will revise all the changes in existing PRs, and duplicate the test to cover old and new usages.
While I'm not simply adding back every test for the old setting, but refine and pick the necessary tests that cover the missing part, by understanding the meaning of the removed test cases.
I think the tests can be removed along with removing the deprecated settings, and I will create an issue for the removal together.
We don't need to worry much about forgetting moving the tests in the future, because they include references to the deprecated setting, and the tests will be failed to compile after the deprecated usage is removed. Even if there is no reference, I will add TODO: in the code. 😄