TestSwitchBurst is unstable

[lhy1024]

Flaky Test

Which jobs are failing

2023-06-15T10:22:47.5222863Z --- FAIL: TestResourceManagerClientTestSuite (55.66s)
2023-06-15T10:22:47.5223456Z     --- FAIL: TestResourceManagerClientTestSuite/TestSwitchBurst (11.46s)
2023-06-15T10:22:47.5223732Z         resource_manager_test.go:535: 
2023-06-15T10:22:47.5224465Z                Error Trace:    /home/runner/work/pd/pd/tests/integrations/mcs/resourcemanager/resource_manager_test.go:535
2023-06-15T10:22:47.5224848Z                Error:          "102.721127ms" is not less than "100ms"
2023-06-15T10:22:47.5225330Z                Test:           TestResourceManagerClientTestSuite/TestSwitchBurst

CI link

https://github.com/tikv/pd/actions/runs/5277548791/jobs/9545734821

Reason for failure (if possible)

Anything else

[HuSharp]

https://github.com/tikv/pd/actions/runs/7220294218/job/19729949910?pr=7493 again

[lhy1024]

https://github.com/tikv/pd/actions/runs/11028564530/job/30629044212?pr=4903

[lhy1024]

https://github.com/tikv/pd/actions/runs/11452910057/job/31864522626

[okJiang]

https://github.com/tikv/pd/actions/runs/11699950625/job/32582940938?pr=8704

    resource_manager_test.go:628: 
            Error Trace:    /home/runner/work/pd/pd/tests/integrations/mcs/resourcemanager/resource_manager_test.go:628
            Error:          "108.883472ms" is not less than "100ms"
            Test:           TestResourceManagerClientTestSuite/TestSwitchBurst

[wuhuizuo]

again in https://github.com/tikv/pd/actions/runs/11568942926/job/32201751159?pr=8660

Ref #8660