Emit scale down metric even when there is no scale down candidates.

[damikag]

What type of PR is this?

/kind bug

What this PR does / why we need it:

Update scale scaleDownInCooldown definition to skip considering zero candidates as a reason to be in scaleDownInCooldown state
Emit scale down metric even when there is no scale down candidates.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

Update scale `scaleDownInCooldown` definition to skip considering zero candidates as a reason to be in `scaleDownInCooldown` state

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: damikag
Once this PR has been reviewed and has the lgtm label, please assign aleksandra-malinowska for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• cluster-autoscaler/OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[k8s-ci-robot]

Hi @damikag. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[jackfrancis]

@damikag this is a significant change to the existing behavior, can you describe why we would want to make this breaking behavioral change? Normally we wouldn't make a change like this without enabling it behind a feature/config flag of some kind

cc @towca @BigDarkClown