cmd: ddl_test modify retryCnt from 5 to 20 (#24662)

[ti-srebot]

cherry-pick #24662 to release-5.0
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/24664

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

git push git@github.com:ti-srebot/tidb.git pr/24664:release-5.0-392df99f04d5

---

What problem does this PR solve?

Issue Number: close #xxx

Problem Summary:

What is changed and how it works?

What's Changed:
When the CI is unstable, tidb-server may take a long time to start. This will cause the ping to fail.
When reaching the retryCnt the integration-dll-test will fatal.

This commit increases the retryCnt to 20 to reduce the impact of the unstable CI.

How it Works:

Related changes

• PR to update pingcap/docs/pingcap/docs-cn:
• Need to cherry-pick to the release branch

Check List

Tests

• No code

Side effects

• Performance regression
  • Consumes more CPU

Release note

• No release note

[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.

To merge this cherry pick, it must first be approved (/lgtm + /merge) by the collaborators.

AFTER it has been approved by collaborators, please ping the release team in a comment to request a cherry pick review.

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[ti-srebot]

/run-all-tests

[ti-srebot]

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

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• AilinKid
• zimulala

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
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[zimulala]

LGTM

[XuHuaiyu]

/merge

[ti-chi-bot]

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

Commit hash: b0c0f48

[ti-chi-bot]

@ti-srebot: Your PR was out of date, I have automatically updated it for you.

At the same time I will also trigger all tests for you:

/run-all-tests

If the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.