DDL: Skip collecting TiFlash status when TiFlash is down (#40872)

[ti-chi-bot]

This is an automated cherry-pick of #40872

What problem does this PR solve?

Issue Number: close #38484

Problem Summary:

What is changed and how it works?

Skip CollectTiFlashStatus when the state of TiFlash store is Down.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
  Two TFlash nodes, keep a TiFlash down and then set tiflash replica. Expect that the available become 1.
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[ti-chi-bot]

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[ti-chi-bot]

@ti-chi-bot: This cherry pick PR is for a release branch and has not yet been approved by release team.
Adding the do-not-merge/cherry-pick-not-approved label.

To merge this cherry pick, it must first be approved by the collaborators.

AFTER it has been approved by collaborators, please ping the release team in a comment to request a cherry pick review.

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[JaySon-Huang]

/close

the bug does not affect release-5.4

[ti-chi-bot]

@JaySon-Huang: Closed this PR.

In response to this:

/close

the bug does not affect release-5.4

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/test-infra repository.