log backup: fix the issue that paused service safepoint not removed (#52106)

[ti-chi-bot]

This is an automated cherry-pick of #52106

What problem does this PR solve?

Issue Number: close #52082

Problem Summary:
stop task didn't remove service safepoint correctly.

What changed and how does it work?

1. set ttl == 0 to make pd service remove this safepoint.

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 the issue that stop log backup didn't clean paused task gc safepoint correctly.

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-05-23 08:32:37.237583128 +0000 UTC m=+2333310.994718703: ☑️ agreed by BornChanger.
• 2024-05-23 10:12:12.98841572 +0000 UTC m=+2339286.745551292: ☑️ agreed by 3pointer.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (release-7.5@3841026). Learn more about missing BASE report.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-7.5     #52250   +/-   ##
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Flag	Coverage Δ
unit	71.9957% <ø> (?)

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Components	Coverage Δ
dumpling	53.9913% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	53.4220% <0.0000%> (?)

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: 3pointer, BornChanger

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