Update e2e test infrastructure

__tests__/e2e-test-csproj/test.csproj

@@ -2,11 +2,11 @@
 
   <PropertyGroup>
     <TargetFramework>$(TEST_TARGET_FRAMEWORK)</TargetFramework>
-
     <IsPackable>false</IsPackable>
   </PropertyGroup>
 
   <ItemGroup>
+    <!-- These packages will be downloaded over the network for testing proxy settings -->
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.5.0-preview-20170810-02" />
     <PackageReference Include="MSTest.TestAdapter" Version="1.1.18" />
     <PackageReference Include="MSTest.TestFramework" Version="1.1.18" />