ttl: fix scan workers shrink (#39860)

[ti-chi-bot]

This is an automated cherry-pick of #39860

Signed-off-by: YangKeao yangkeao@chunibyo.icu

What problem does this PR solve?

Issue Number: close #39859

Problem Summary:

What is changed and how it works?

After shrinking the scan workers, poll the result of left workers and use the result to update the state of a job.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• YangKeao
• hawkingrei

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[YangKeao]

LGTM

[hawkingrei]

/merge

[hawkingrei]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 6166ecc

[YangKeao]

/run-unit-test

[YangKeao]

/run-unit-test

[YangKeao]

TestConcurrentDDLSwitch failed.

[hawkingrei]

TestConcurrentDDLSwitch failed.

It often fails. Please try again.

[ti-chi-bot]

@ti-chi-bot: Your PR was out of date, I have automatically updated it for you.

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