disttask: fix bug when owner change

[ywqzzy]

What problem does this PR solve?

Issue Number: close #46014

Problem Summary:
It is possible that 2 dispatcher coexist on different server.
Then these 2 dispatcher dispatched subtasks twice.

What is changed and how it works?

Before dispatch task, check the dispatcher is the owner.

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

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[tiprow]

Hi @ywqzzy. Thanks for your PR.

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[codecov]

Codecov Report

Merging #46054 (7703e41) into master (c34f6fc) will decrease coverage by 2.1204%.
Report is 1 commits behind head on master.
The diff coverage is 30.0000%.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #46054        +/-   ##
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- Coverage   74.7608%   72.6404%   -2.1204%     
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  Files          1293       1300         +7     
  Lines        398103     400167      +2064     
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- Hits         297625     290683      -6942     
- Misses        81108      90992      +9884     
+ Partials      19370      18492       -878     

Flag	Coverage Δ
integration	25.5613% <30.0000%> (-20.7016%)	⬇️

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

Components	Coverage Δ
dumpling	54.0444% <ø> (ø)
parser	85.0656% <ø> (ø)
br	47.6395% <ø> (-16.8901%)	⬇️

[ti-chi-bot]

@ywqzzy: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
idc-jenkins-ci-tidb/unit-test	7703e41	link	true	/test unit-test
idc-jenkins-ci-tidb/build	7703e41	link	true	/test build

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[lance6716]

what if the owner is dropped just after this check? There is always an interval between time of check to time of use. Can we add a version to transactional storage to detect it?

[ywqzzy]

Good point!