React to HttpAbstractions change: No features in .Internal namespace

- see issue aspnet/HttpAbstractions#561 and pull aspnet/HttpAbstractions#589

Author: dougbu

src/Microsoft.AspNetCore.CookiePolicy/CookiePolicyMiddleware.cs

@@ -5,6 +5,7 @@
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Http.Features;
 using Microsoft.AspNetCore.Http.Features.Internal;
 using Microsoft.Extensions.Options;
 

test/Microsoft.AspNetCore.CookiePolicy.Test/CookiePolicyTests.cs

@@ -7,7 +7,6 @@
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Http.Features;
-using Microsoft.AspNetCore.Http.Features.Internal;
 using Microsoft.AspNetCore.TestHost;
 using Xunit;
 
@@ -277,7 +276,7 @@ public async Task Execute(TestServer server)
         }
 
         private async Task RunTest(
-            string path, 
+            string path,
             CookiePolicyOptions cookiePolicy,
             RequestDelegate configureSetup,
             params RequestTest[] tests)