Fix race

Author: Youssef1313

src/Platform/Microsoft.Testing.Platform/Hosts/CommonTestHost.cs

@@ -69,7 +69,11 @@ public async Task<int> RunAsync()
             await DisposeServiceProviderAsync(ServiceProvider, isProcessShutdown: true);
             await DisposeHelper.DisposeAsync(ServiceProvider.GetService<FileLoggerProvider>());
             await DisposeHelper.DisposeAsync(PushOnlyProtocol);
-            await DisposeHelper.DisposeAsync(ServiceProvider.GetTestApplicationCancellationTokenSource());
+
+            // This is intentional that we are not disposing the CTS.
+            // An unobserved task exception could be raised after the dispose, and we want to use OutputDevice there
+            // which needs CTS down the path.
+            // await DisposeHelper.DisposeAsync(ServiceProvider.GetTestApplicationCancellationTokenSource());
         }
 
         if (testApplicationCancellationToken.IsCancellationRequested)

src/Platform/Microsoft.Testing.Platform/Hosts/ServerTestHost.cs

@@ -660,6 +660,11 @@ public void Dispose()
     {
         // Note: The lifetime of the _reader/_writer should be currently handled by the RunAsync()
         // We could consider creating a stateful engine that has the lifetime == server connection UP.
+        if (!ServiceProvider.GetUnhandledExceptionsPolicy().FastFailOnFailure)
+        {
+            AppDomain.CurrentDomain.UnhandledException -= OnCurrentDomainUnhandledException;
+            TaskScheduler.UnobservedTaskException -= OnTaskSchedulerUnobservedTaskException;
+        }
     }
 
     internal async Task SendTestUpdateCompleteAsync(Guid runId)