Add retries to helix failures and re-enable helix as a required workload (#9221)

eng/helix/helix.proj

@@ -13,12 +13,13 @@
     <HelixBuild>private-$(USERNAME)</HelixBuild>
     <HelixBuild Condition=" '$(USERNAME)' == '' ">private-$(USER)</HelixBuild>
     <HelixBuild Condition=" '$(CI)' == 'true' ">$(BUILD_BUILDNUMBER)</HelixBuild>
-    <WaitForWorkItemCompletion Condition=" '$(CI)' == 'true' ">false</WaitForWorkItemCompletion>
-    <FailOnMissionControlTestFailure>false</FailOnMissionControlTestFailure>
+    <WaitForWorkItemCompletion Condition=" '$(CI)' == 'true' ">true</WaitForWorkItemCompletion>
+    <FailOnMissionControlTestFailure>true</FailOnMissionControlTestFailure>
     <EnableAzurePipelinesReporter>true</EnableAzurePipelinesReporter>
     <IsExternal>true</IsExternal>
     <Creator>aspnetcore</Creator>
     <SkipInvalidConfigurations>true</SkipInvalidConfigurations>
+    <MaxRetryCount Condition="'$(MaxRetryCount)' == ''">4</MaxRetryCount>
   </PropertyGroup>
 
   <Target Name="Gather" BeforeTargets="Build">

src/Http/Http.Abstractions/test/PathStringTests.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;

src/Servers/Kestrel/test/Interop.FunctionalTests/Interop.FunctionalTests.csproj

@@ -6,6 +6,8 @@
     <TestGroupName>Interop.FunctionalTests</TestGroupName>
     <!-- WebDriver is not strong named, so this test assembly cannot be strong-named either. -->
     <SignAssembly>false</SignAssembly>
+    <!-- See: https://github.com/aspnet/AspNetCore/issues/7299 -->
+    <BuildHelixPayload>false</BuildHelixPayload>
   </PropertyGroup>
 
   <ItemGroup>