br: fix broken integration test (#36411)

[ti-srebot]

cherry-pick #36411 to release-5.4
You can switch your code base to this Pull Request by using git-extras:

# In tidb repo:
git pr https://github.com/pingcap/tidb/pull/37326

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

git push git@github.com:ti-srebot/tidb.git pr/37326:release-5.4-656b5a5e8050

---

What problem does this PR solve?

Issue Number:

Problem Summary:
After #32169 merged. br will panic in br_incremental_only_ddl tests.
After tikv/tikv#12958 merged. br_other tests will failed due to backup path has changed.

What is changed and how it works?

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

[ti-chi-bot]

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[ti-chi-bot]

@ti-srebot: This cherry pick PR is for a release branch and has not yet been approved by release team.
Adding the do-not-merge/cherry-pick-not-approved label.

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[ti-srebot]

/run-all-tests

[ti-srebot]

@3pointer you're already a collaborator in bot's repo.