downgrade System.Threading.Overlapped to fix build

src/Microsoft.Net.Http.Server/project.json

@@ -20,7 +20,7 @@
                 "System.Security.Claims": "4.0.1-beta-*",
                 "System.Security.Cryptography.X509Certificates": "4.0.0-beta-*",
                 "System.Security.Principal.Windows": "4.0.0-beta-*",
-                "System.Threading.Overlapped": "4.0.1-beta-*"
+                "System.Threading.Overlapped": "4.0.0"
             }
         }
     }