Unstable test: AsyncPumpReleasedAfterExecution

From this build:

2018-12-17T17:48:40.1931861Z Failed   AsyncPumpReleasedAfterExecution(throwInValueFactory: False)
2018-12-17T17:48:40.1944221Z Error Message:
2018-12-17T17:48:40.1944590Z  Assert.False() Failure
2018-12-17T17:48:40.1944766Z Expected: False
2018-12-17T17:48:40.1944822Z Actual:   True
2018-12-17T17:48:40.1944897Z Stack Trace:
2018-12-17T17:48:40.1944985Z    at Microsoft.VisualStudio.Threading.Tests.AsyncLazyTests.<AsyncPumpReleasedAfterExecution>d__8.MoveNext() in E:\A\_work\326\s\src\Microsoft.VisualStudio.Threading.Tests\AsyncLazyTests.cs:line 219
2018-12-17T17:48:40.1945117Z --- End of stack trace from previous location where exception was thrown ---
2018-12-17T17:48:40.1945187Z    at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
2018-12-17T17:48:40.1945273Z    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
2018-12-17T17:48:40.1945347Z    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
2018-12-17T17:48:40.1945420Z    at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task)
2018-12-17T17:48:40.1945502Z    at System.Runtime.CompilerServices.TaskAwaiter.GetResult()
2018-12-17T17:48:40.1945571Z --- End of stack trace from previous location where exception was thrown ---
2018-12-17T17:48:40.1945658Z    at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
2018-12-17T17:48:40.1945726Z    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
2018-12-17T17:48:40.1945831Z    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
2018-12-17T17:48:40.1945905Z    at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task)
2018-12-17T17:48:40.1945972Z    at System.Runtime.CompilerServices.TaskAwaiter.GetResult()
2018-12-17T17:48:40.1946056Z --- End of stack trace from previous location where exception was thrown ---
2018-12-17T17:48:40.1946126Z    at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
2018-12-17T17:48:40.1946209Z    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
2018-12-17T17:48:40.1946283Z    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
2018-12-17T17:48:40.1946370Z    at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task)
2018-12-17T17:48:40.1946437Z    at System.Runtime.CompilerServices.TaskAwaiter.GetResult()

Start with AsyncLazyTests.cs at line 219 and run AsyncPumpReleasedAfterExecution for both throwInValueFactory values. Investigate why the assertion intermittently reports the async pump as released, then verify the test completes reliably without the reported failure.