Fix NPE in vpa-updater when Pod owner isn't scalable

[voelzmo]

What type of PR is this?

/kind bug

What this PR does / why we need it:

The method ctrlFetcher.FindTopMostWellKnownOrScalable returns nil without an additional error, when there is no owner that is either scalable (implementing the /scale subresource) or is well-known. In this case, just skip the current Pod, as it cannot be controlled by a VPA.

Which issue(s) this PR fixes:

Fixes #6709

Special notes for your reviewer:

This PR adds two tests to make sure this cannot regress:

• vertical-pod-autoscaler/pkg/target/controller_fetcher/controller_fetcher_test.go gets the new testcase custom resource with no scale subresource which ensures that for a Pod, which is not under VPA control and has an ownerRef to a custom resource that doesn't implement /scale, the method FindTopMostWellKnownOrScalable returns nil, nil
• vertical-pod-autoscaler/pkg/utils/vpa/api_test.go gets an additional test assertion which uses a fake controllerFetcher, which always returns nil to make sure that GetControllingVPAForPod can deal with a nil, nil response from ctrlFetcher.FindTopMostWellKnownOrScalable

Does this PR introduce a user-facing change?

Fix: NPE in vpa-updater when Pods have an `ownerReference` to a Custom Resource which doesn't implement the `/scale` subresource

[kwiesmueller]

Does it replicate if we just make the owner be a ConfigMap or any other resource?

[kwiesmueller]

I would prefer a test, otherwise lgtm.

[voelzmo]

Does it replicate if we just make the owner be a ConfigMap or any other resource?

Great Idea! I've replicated it by setting the ownerReference to kind: ConfigMap. I'll add a test case and comment in there, why we would be doing a seemingly stupid thing :)

[voelzmo]

@kwiesmueller I ended up taking a simpler approach, outlined in the PR original comment above. WDYT?

[kwiesmueller]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: kwiesmueller, voelzmo

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[voelzmo]

/cherry-pick vpa-release-1.1

Edit: seems like the bot doesn't pick this up, I ended up cherry-picking it manually to vpa-release-1.1

[akloss-cibo]

I hoped to update to 1.1.0 to see if #6705 is addressed there, but I'm stuck behind this. Is there a new release planned soon?

[kwiesmueller]

We'll work on a 1.1.1 release this week.

[kwiesmueller]

Released as https://github.com/kubernetes/autoscaler/releases/tag/vertical-pod-autoscaler-1.1.1

[nikimanoledaki]

I hoped to update to 1.1.0 to see if #6705 is addressed there, but I'm stuck behind this. Is there a new release planned soon?

Hi! Just saw that the other issue was referenced here. @akloss-cibo do you have an update on whether #6705 was addressed for you? More info on your theory around this would be appreciated too. Perhaps best to speak in the open issue rather than here :) Thank you!