test: align with TiDB clustered index behaviour (#1538)

[ti-srebot]

cherry-pick #1538 to release-2.0
You can switch your code base to this Pull Request by using git-extras:

# In dm repo:
git pr https://github.com/pingcap/dm/pull/1539

After apply modifications, you can push your change to this PR via:

git push git@github.com:ti-srebot/dm.git pr/1539:release-2.0-415e713db316

---

What problem does this PR solve?

revert some of #1522

What is changed and how it works?

Check List

Tests

• No code

Related changes

• Need to cherry-pick to the release branch

[lance6716]

/lgtm

[lance6716]

/run-all-tests

[GMHDBJD]

/lgtm

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• GMHDBJD
• lance6716

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[lance6716]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Details

Commit hash: 83e52dd