client/tso: fix the bug that TSO may hang when switching mode

[JmPotato]

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]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• CabinfeverB
• HuSharp

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[codecov]

Codecov Report

Merging #7937 (f44cd5a) into master (1331148) will increase coverage by 0.04%.
Report is 1 commits behind head on master.
The diff coverage is 83.33%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7937      +/-   ##
==========================================
+ Coverage   73.47%   73.51%   +0.04%     
==========================================
  Files         436      436              
  Lines       48349    48362      +13     
==========================================
+ Hits        35523    35554      +31     
+ Misses       9765     9751      -14     
+ Partials     3061     3057       -4     

Flag	Coverage Δ
unittests	73.51% <83.33%> (+0.04%)	⬆️

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

[CabinfeverB]

rest LGTM

[CabinfeverB]

/merge

[ti-chi-bot]

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/run-all-tests

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[ti-chi-bot]

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

Commit hash: 0c3741d

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.1: #7941.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.0: #7942.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.5: #7943.