disttask: fix owner change flaky test

[ywqzzy]

What problem does this PR solve?

Issue Number: close #46014

Problem Summary:
Subtask in tests are not reentrant.

What is changed and how it works?

Use map instead of atomic.Int64

Check List

Tests

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

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

[tiprow]

Hi @ywqzzy. Thanks for your PR.

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[codecov]

Codecov Report

Merging #46075 (73f21c0) into master (c34f6fc) will decrease coverage by 2.0570%.
Report is 12 commits behind head on master.
The diff coverage is n/a.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #46075        +/-   ##
================================================
- Coverage   74.7608%   72.7038%   -2.0570%     
================================================
  Files          1293       1300         +7     
  Lines        398103     399891      +1788     
================================================
- Hits         297625     290736      -6889     
- Misses        81108      90707      +9599     
+ Partials      19370      18448       -922     

Flag	Coverage Δ
integration	25.7527% <ø> (-20.5102%)	⬇️
unit	73.3759% <ø> (+0.0299%)	⬆️

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

Components	Coverage Δ
dumpling	54.0444% <ø> (ø)
parser	85.0548% <ø> (-0.0109%)	⬇️
br	47.6243% <ø> (-16.9053%)	⬇️

[GMHDBJD]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: GMHDBJD, hawkingrei

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-08-15 03:47:54.432723834 +0000 UTC m=+602838.981739823: ☑️ agreed by GMHDBJD.
• 2023-08-15 04:00:38.587567045 +0000 UTC m=+603603.136583018: ☑️ agreed by hawkingrei.