fix: support rolling update lws with 1 replica

[congcongke]

What type of PR is this?

/kind bug

What this PR does / why we need it

In my opinion, the replica should be decreased when the (unready replica < maxSurge). It means the rolling update is in progress and newly created one is partly stable.

Which issue(s) this PR fixes

Background:

1. LWS is in running with 1 replica, 25% maxSurge and 25% minUnavailable
2. Update the image or cpu quota of LWS

What I want:

1. Scale Statefulset up to 2 replica, with the second instance with new image.
2. After the second one is in running, update the first instance
3. Scale Statefulset down to 1 replica, with all the instance updated

Actual

1. The replica of Statefulset is stay at 1 with partition is set to 1

Special notes for your reviewer

Does this PR introduce a user-facing change?

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: congcongke
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[k8s-ci-robot]

Hi @congcongke. Thanks for your PR.

I'm waiting for a kubernetes-sigs 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.

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[netlify]

✅ Deploy Preview for kubernetes-sigs-lws canceled.

Name	Link
🔨 Latest commit	4b749ac
🔍 Latest deploy log	https://app.netlify.com/sites/kubernetes-sigs-lws/deploys/6819c71bacc47c00088e9ecf

[Edwinhr716]

/ok-to-test

[kerthcet]

What's the status here? @Edwinhr716

[Edwinhr716]

Only saw the duplication of tests, haven't really taken a look at it or thought about if it is something we want

[k8s-ci-robot]

PR needs rebase.

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[k8s-ci-robot]

@congcongke: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-lws-test-e2e-main-gang-scheduling	4b749ac	link	true	/test pull-lws-test-e2e-main-gang-scheduling
pull-lws-test-e2e-main-1-33	4b749ac	link	true	/test pull-lws-test-e2e-main-1-33

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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. I understand the commands that are listed here.