Add unit test for Node controller

[cadenmarchese]

Which issue this PR addresses:

https://msazure.visualstudio.com/AzureRedHatOpenShift/_workitems/edit/10227470/

What this PR does / why we need it:

Adds some coverage to the Node controller to ensure we're adding and reading our annotations properly. Also adds a const.go file for the node package since it's standard practice among other operator controllers.

Test plan for issue:

make test-go
go test -v

Is there any documentation that needs to be updated for this PR?

No

[troy0820]

Just a few nits. You have coverage over all these functions but because you are doing a table test you could create a test that tests every condition in the isDraining function. So the annotations to see if they are blank, etc. That way the confidence of this function will increase as you tested that each condition can create the return value necessary.

[m1kola]

I think we need the following tests for this controller:

1. Test individual functions such as isDraining with all possible scenarios as Troy suggested.
2. Make isDraining mockable and test the controller via Reconcile. This way we don't have to meet all the conditions inside isDraining in test data and don't have to care about implementation of isDraining: we just make it returns either true or false and cover these code paths.

I'm happy for these two things to be submitted in a separate PRs, if you prefer. But we definitely need the second point - without it there is a lot of code (contriller's main logic) without coverage.

[cadenmarchese]

@m1kola @troy0820 I agree we should test via Reconcile, and I had previously attempted to do it unsuccessfully, but I can work on it more. I have addressed the other comments and squashed commits, so we can either merge with followup issue to change to Reconcile, or else I will continue to work on it via this PR - whatever is preferred.

[m1kola]

@cadenmarchese let's finish covering individual functions in this PR and cover Reconcile in a separate PR.

[m1kola]

Looks good. Only one small suggestion for TestSetAnnotation.

[m1kola]

Looks good. We still need to cover main logic of this controller (Reconcile method). Let's do it in a separate PR.

Troy's feedback was addressed, I believe. Dismissing the review.