Fix flakey integration test cases.

[asddongmen]

What did you do?

Some integration tests are unstable, which severely impacts the efficiency of PRmerging and reduces everyone's work efficiency.
Therefore, we must fix them as soon as possible. If you identify any unstable integration tests, please open a new issue and then add the link of the newly - created issue to this issue. We need to resolve them promptly! Thank you!

Unstable Integration Case List

• Integration test case region_merge is unstable. #1119
• Integration test bank is unstable #1121
• Integration test multi_tables_ddl is unstable. #1127
• Integration test move_table is unstable. #1128

What did you expect to see?

No response

What did you see instead?

as title.

Versions of the cluster

as title.