[Flaky test] Microsoft.Build.UnitTests.BackEnd.TaskBuilder_Tests.CanceledTasksDoNotLogMSB4181

[surayya-MS]

While working on #9621 I came across this flaky test. It doesn't flake that often. The last 4 failed builds have same error message

Shouldly.ShouldAssertException : isSubmissionComplated\r\n    should be\r\nTrue\r\n    but was\r\nFalse\r\n\r\nAdditional Info:\r\n    Waiting for that the build submission is completed failed in the timeout period 2000 ms.

and stack trace

at Microsoft.Build.UnitTests.BackEnd.TaskBuilder_Tests.CanceledTasksDoNotLogMSB4181() in D:\a\1\s\src\Build.UnitTests\BackEnd\TaskBuilder_Tests.cs:line 189

Sample failing build:
https://dev.azure.com/dnceng-public/public/_build/results?buildId=525000&view=ms.vss-test-web.build-test-results-tab&runId=12351978&resultId=104181&paneView=history

[surayya-MS]

This test was previously reported as flaky and there was an attempt to fix it #9298

[JaynieBai]

Still failed in latest build https://dev.azure.com/dnceng-public/public/_build/results?buildId=588018&view=ms.vss-test-web.build-test-results-tab&runId=14181820&resultId=104008

Error message
Shouldly.ShouldAssertException : isSubmissionComplated\r\n should be\r\nTrue\r\n but was\r\nFalse\r\n\r\nAdditional Info:\r\n Waiting for that the build submission is completed failed in the timeout period 2000 ms.

Stack trace
at Microsoft.Build.UnitTests.BackEnd.TaskBuilder_Tests.CanceledTasksDoNotLogMSB4181() in D:\a\1\s\src\Build.UnitTests\BackEnd\TaskBuilder_Tests.cs:line 189
at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)
at System.Reflection.MethodBaseInvoker.InvokeWithNoArgs(Object obj, BindingFlags invokeAtt

[f-alizada]

Another record of failed test: https://dev.azure.com/dnceng-public/public/_build/results?buildId=646890&view=ms.vss-test-web.build-test-results-tab