subsequent block has data - IsEnd is false

Resolves #249

src/Microsoft.AspNet.Server.Kestrel/Infrastructure/MemoryPoolIterator2.cs

@@ -55,7 +55,7 @@ namespace Microsoft.AspNet.Server.Kestrel.Infrastructure
                     {
                         if (block.Start < block.End)
                         {
-                            return true;
+                            return false; // subsequent block has data - IsEnd is false
                         }
                     }
                     return true;