[helm] PodDisruptionBudget spec logic update for controller.maxUnavailable

[balonik]

What this PR does / why we need it:

Allow to specify both controller.minAvailable and controller.maxUnavailable. minAvailable will be ignored if maxUnavailable is set. Removes the need to set minAvailable: null in chart's values if maxUnavailable is desired instead.
This is especially helpful when using Kustomize which handles null values in a special way (ref: kubernetes-sigs/kustomize#4628) and therefore it's impossible to "unset" controller.minAvailable from chart's default values. Related issue in Flux CD fluxcd/kustomize-controller#372

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• CVE Report (Scanner found CVE and adding report)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation only

Which issue/s this PR fixes

fixes #9625

How Has This Been Tested?

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I've read the CONTRIBUTION guide
• I have added unit and/or e2e tests to cover my changes.
• All new and existing tests passed.
• Added Release Notes.

NONE

[k8s-ci-robot]

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[balonik]

This change does NOT break existing behavior.

Examples:
default values controller.minAvailable: 1, controller.maxUnavailable unset (commented out)
expected: minAvailable: 1
got: minAvailable: 1

---
# Source: ingress-nginx/templates/controller-poddisruptionbudget.yaml
apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  labels:
    helm.sh/chart: ingress-nginx-4.6.0
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/instance: release-name
    app.kubernetes.io/version: "1.7.0"
    app.kubernetes.io/part-of: ingress-nginx
    app.kubernetes.io/managed-by: Helm
    app.kubernetes.io/component: controller
  name: release-name-ingress-nginx-controller
  namespace: ingress
spec:
  selector:
    matchLabels:
      app.kubernetes.io/name: ingress-nginx
      app.kubernetes.io/instance: release-name
      app.kubernetes.io/component: controller
  minAvailable: 1

controller.minAvailable: null, controller.maxUnavailable: 1 (currently only way how to do it)
expected: maxUnavailable: 1
got: maxUnavailable: 1

---
# Source: ingress-nginx/templates/controller-poddisruptionbudget.yaml
apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  labels:
    helm.sh/chart: ingress-nginx-4.6.0
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/instance: release-name
    app.kubernetes.io/version: "1.7.0"
    app.kubernetes.io/part-of: ingress-nginx
    app.kubernetes.io/managed-by: Helm
    app.kubernetes.io/component: controller
  name: release-name-ingress-nginx-controller
  namespace: ingress
spec:
  selector:
    matchLabels:
      app.kubernetes.io/name: ingress-nginx
      app.kubernetes.io/instance: release-name
      app.kubernetes.io/component: controller
  maxUnavailable: 1

controller.minAvailable: 1, controller.maxUnavailable: 1 (new way how it can be done)
expected: maxUnavailable: 1
got: maxUnavailable: 1

---
# Source: ingress-nginx/templates/controller-poddisruptionbudget.yaml
apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  labels:
    helm.sh/chart: ingress-nginx-4.6.0
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/instance: release-name
    app.kubernetes.io/version: "1.7.0"
    app.kubernetes.io/part-of: ingress-nginx
    app.kubernetes.io/managed-by: Helm
    app.kubernetes.io/component: controller
  name: release-name-ingress-nginx-controller
  namespace: ingress
spec:
  selector:
    matchLabels:
      app.kubernetes.io/name: ingress-nginx
      app.kubernetes.io/instance: release-name
      app.kubernetes.io/component: controller
  maxUnavailable: 1

[balonik]

any feedback would be greatly appreciated

[strongjz]

@balonik can you rebase to get the 1.27 tests?

Looks good to me, just need to update for the tests.

[strongjz]

/ok-to-test

[balonik]

@strongjz rebased and tests passed

[strongjz]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: balonik, strongjz

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