Add a missing constant for NO_ROUTE

Closes #1331

Author: michaelklishin

projects/RabbitMQ.Client/client/framing/Constants.cs

@@ -49,6 +49,8 @@ public static class Constants
         public const int ReplySuccess = 200;
         ///<summary>(= 311)</summary>
         public const int ContentTooLarge = 311;
+        ///<summary>(= 312)</summary>
+        public const int NoRoute = 312;        
         ///<summary>(= 313)</summary>
         public const int NoConsumers = 313;
         ///<summary>(= 320)</summary>