client/tso: fix the bug that TSO may hang when switching mode (#7937)

[ti-chi-bot]

This is an automated cherry-pick of #7937

What problem does this PR solve?

Issue Number: ref #7849.

What is changed and how does it work?

Because the old `(*tsoClient).dispatchRequest` only checked the request's context,
this could potentially cause a `tsoRequest` to be sent to a batch channel that has already
finished `revokePendingTokenRequest`, thus being left there forever without returning.

Check List

Tests

• Unit test
• Integration test

Release note

None.

[ti-chi-bot]

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