test(ticdc): fix bank failure caused by wrong snapshot in db session (#8212)

[ti-chi-bot]

This is an automated cherry-pick of #8212

What problem does this PR solve?

Issue Number: close #8211

What is changed and how it works?

*sql.DB holds a connection pool, it returns a random idle connection, in the bank test we need to ensure the database connection has the same snapshot during verification.

Check List

Tests

• Integration test

Questions

Will it cause performance regression or break compatibility?

Do you need to update user documentation, design documentation or monitoring documentation?

Release note

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has not been approved.

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.

[ti-chi-bot]

@ti-chi-bot: 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 by the collaborators.

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

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 kubernetes/test-infra repository.

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (release-6.1@8923c92). Click here to learn what that means.
The diff coverage is n/a.

❗ Current head f638c1c differs from pull request most recent head 7509bae. Consider uploading reports for the commit 7509bae to get more accurate results

Additional details and impacted files

Flag	Coverage Δ
cdc	63.9646% <0.0000%> (?)
dm	57.6990% <0.0000%> (?)
engine	66.6056% <0.0000%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

@@               Coverage Diff                @@
##             release-6.1      #8276   +/-   ##
================================================
  Coverage               ?   60.8653%           
================================================
  Files                  ?        895           
  Lines                  ?     123535           
  Branches               ?          0           
================================================
  Hits                   ?      75190           
  Misses                 ?      41990           
  Partials               ?       6355