br: fix Log Backup unexpected paused when adding a already long-running task (#53695)

[ti-chi-bot]

This is an automated cherry-pick of #53695

What problem does this PR solve?

Issue Number: close #53561

Problem Summary:

What changed and how does it work?

Now, advancer will sync checkpoint with pd when adding a new task

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.

Fix Log Backup unexpected paused when adding a long-run task

[RidRisR]

/test check-dev

[tiprow]

@RidRisR: No presubmit jobs available for pingcap/tidb@release-7.1

In response to this:

/test check-dev

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[RidRisR]

/test check-dev2

[tiprow]

@RidRisR: No presubmit jobs available for pingcap/tidb@release-7.1

In response to this:

/test check-dev2

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.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (release-7.1@ba0d06e). Learn more about missing BASE report.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-7.1     #53948   +/-   ##
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  Partials               ?      17834           

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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Needs approval from an approver in each of these files:

• OWNERS [Leavrth,YuJuncen]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-07-18 05:30:39.586486649 +0000 UTC m=+504661.577428120: ☑️ agreed by YuJuncen.
• 2024-07-18 05:54:52.399296149 +0000 UTC m=+506114.390237619: ☑️ agreed by Leavrth.