br/operator: fix stuck when terminating (#52264)

[ti-chi-bot]

This is an automated cherry-pick of #52264

What problem does this PR solve?

Issue Number: close #52243

Problem Summary:
When exiting due to error, we are waiting from the client to finish before receiving from the output channel. In this case, the output channel may be full and blocks the exit procedure.

What changed and how does it work?

We will poll from both the request exit result and the exit channel.

Check List

Tests

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

  • I checked and no code files have been changed.

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.

Fixed an issue where init pod may get stuck when encountering connective errors.

[YuJuncen]

/build

[YuJuncen]

/test unit-test

[tiprow]

@YuJuncen: No presubmit jobs available for pingcap/tidb@release-6.5

In response to this:

/test unit-test

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[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-6.5@9815b45). Click here to learn what that means.
The diff coverage is 87.0967%.

Additional details and impacted files

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: BornChanger, Leavrth

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• OWNERS [Leavrth]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-04-11 06:51:09.717686822 +0000 UTC m=+1117931.245227532: ☑️ agreed by Leavrth.
• 2024-04-17 14:14:38.195167018 +0000 UTC m=+433897.306213468: ☑️ agreed by BornChanger.