client: revise client if mismatch leader id

[Yisaer]

What problem does this PR solve?

After transfer pd leader, the pd client may meet mismatch leader id several times during request global tso.

What is changed and how it works?

This request make mismatch error appearing at most once after transferring pd leader.

Check List

Tests

• Unit test

Release note

• No release note

[codecov]

Codecov Report

Merging #3432 (451e4cb) into master (d28e248) will decrease coverage by 0.07%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master    #3432      +/-   ##
==========================================
- Coverage   75.16%   75.08%   -0.08%     
==========================================
  Files         244      244              
  Lines       23509    23523      +14     
==========================================
- Hits        17670    17662       -8     
- Misses       4274     4290      +16     
- Partials     1565     1571       +6     

Flag	Coverage Δ
unittests	75.08% <66.66%> (-0.08%)	⬇️

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

Impacted Files	Coverage Δ
client/client.go	64.56% <65.00%> (-0.38%)	⬇️
server/grpc_service.go	58.43% <100.00%> (+1.16%)	⬆️
pkg/etcdutil/etcdutil.go	84.70% <0.00%> (-3.53%)	⬇️
server/schedulers/random_merge.go	60.00% <0.00%> (-3.34%)	⬇️
server/tso/allocator_manager.go	76.46% <0.00%> (-3.01%)	⬇️
server/schedule/operator/step.go	67.44% <0.00%> (-1.67%)	⬇️
pkg/btree/btree.go	85.30% <0.00%> (-0.97%)	⬇️
server/handler.go	41.97% <0.00%> (-0.50%)	⬇️
server/server.go	72.44% <0.00%> (-0.31%)	⬇️
server/tso/global_allocator.go	78.03% <0.00%> (ø)
... and 5 more

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[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• JmPotato
• rleungx

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[Yisaer]

/merge

[ti-chi-bot]

@Yisaer: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

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[ti-chi-bot]

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

Commit hash: cd43f95