test(dm): fix unsteable test TestRedirectRequestToLeader (#4556)

[ti-chi-bot]

This is an automated cherry-pick of #4556

What problem does this PR solve?

Issue Number: close #4554

What is changed and how it works?

send reuest after master ready

Check List

Tests

• Unit test

Code changes

Side effects

Related changes

Release note

`None`.

[ti-chi-bot]

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[Ehco1996]

/merge

[ti-chi-bot]

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

Commit hash: af9131b

[Ehco1996]

/merge

[Ehco1996]

/assign @nongfushanquan
🧡🧡🧡🧡🧡

[lance6716]

/merge

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