test: remove duplicated code

[okJiang]

What problem does this PR solve?

Issue Number: Ref #4399

What is changed and how does it work?

Check List

Tests

• Unit test
• Integration test

Release note

None.

[okJiang]

/retest

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 75.22%. Comparing base (36cc3f4) to head (32ae8b0). Report is 1 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #8820 +/- ## ========================================== + Coverage 75.21% 75.22% +0.01% ========================================== Files 456 456 Lines 71608 71608 ========================================== + Hits 53857 53869 +12 + Misses 14317 14308 -9 + Partials 3434 3431 -3 ``` | [Flag](https://app.codecov.io/gh/tikv/pd/pull/8820/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tikv) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/tikv/pd/pull/8820/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tikv) | `75.22% <ø> (+0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tikv#carryforward-flags-in-the-pull-request-comment) to find out more.

---

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[ti-chi-bot[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: JmPotato, rleungx

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/tikv/pd/blob/master/OWNERS)~~ [JmPotato,rleungx] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[ti-chi-bot[bot]]

[LGTM Timeline notifier]

Timeline:

• 2024-11-18 07:20:49.134450171 +0000 UTC m=+859211.325319162: :ballot_box_with_check: agreed by JmPotato.
• 2024-11-18 07:48:21.161263803 +0000 UTC m=+860863.352132800: :ballot_box_with_check: agreed by rleungx.

[okJiang]

/retest

[okJiang]

/retest