ddl: fix some unit test funcion that can't run independently

[tiancaiamao]

What problem does this PR solve?

Issue Number: close #31085

Problem Summary:

Some test cases can't run independently:

make ut X='run ddl TestRenameTables'

or

make failpoint-enable;
cd ddl;
go test -run TestRenameTables

It reports an error "[ddl:-1]failed to notify PD the placement rules: infoSyncer is not initialized"

What is changed and how it works?

When the test case run with others, the global variable is initialized by other test cases

tidb/domain/infosync/info.go

Lines 168 to 170 in 61d13b5

	func setGlobalInfoSyncer(is *InfoSyncer) {
	globalInfoSyncer.Store(is)
	}

This is a workaround to make it possible to run the single test case.

Modification on tools/check/ut.go is unrelated to this fix, it just make the output easier for debugging.

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

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• bb7133
• hawkingrei

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

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

Reviewer can indicate their review by submitting an approval review.
Reviewer can cancel approval by submitting a request changes review.

[tiancaiamao]

It's for #30822

[sre-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/1d30629bdf55fccc3efc55fd9b0b548b0edd2e2b

[tiancaiamao]

/run-check_dev_2

[hawkingrei]

Please remove this empty line

[bb7133]

LGTM

[bb7133]

/merge

[ti-chi-bot]

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

Commit hash: 4aa055f

[ti-chi-bot]

@tiancaiamao: Your PR was out of date, I have automatically updated it for you.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