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

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-7.5@de2293d). Click here to learn what that means.
The diff coverage is 68.7500%.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-7.5     #50170   +/-   ##
================================================
  Coverage               ?   73.6251%           
================================================
  Files                  ?       1404           
  Lines                  ?     421921           
  Branches               ?          0           
================================================
  Hits                   ?     310640           
  Misses                 ?      91866           
  Partials               ?      19415           

Flag	Coverage Δ
unit	73.6251% <68.7500%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	53.9913% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	53.8069% <0.0000%> (?)

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: you06, zyguan

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• OWNERS [you06,zyguan]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-02-20 03:22:05.228308447 +0000 UTC m=+327413.975931557: ☑️ agreed by you06.
• 2024-02-20 03:23:28.106992643 +0000 UTC m=+327496.854615749: ☑️ agreed by zyguan.