fix: check kill signal against 0 (#50029)

[ti-chi-bot]

This is an automated cherry-pick of #50029

What problem does this PR solve?

Issue Number: ref #49643

Problem Summary:

Previously the kill signal was checked against 1, however TiDB uses non-zero values to indicate a kill signal.

What changed and how does it work?

Check List

Tests

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

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]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cfzjywxk, zyguan

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• OWNERS [cfzjywxk,zyguan]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-02-28 01:43:42.830357615 +0000 UTC m=+1012711.577980748: ☑️ agreed by cfzjywxk.
• 2024-02-28 02:37:08.8858977 +0000 UTC m=+1015917.633520811: ☑️ agreed by zyguan.

[ekexium]

/retest

[ekexium]

/retest

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-7.1@f942e74). Click here to learn what that means.
The diff coverage is 52.3809%.

Additional details and impacted files

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