Implement handling of error unauthorized by client forwarding request to remote tcp service. Bubble this up as a 401 to the caller

http/service.go

@@ -1103,6 +1103,10 @@ func (s *Service) execute(w http.ResponseWriter, r *http.Request) {
 		}
 
 		results, resultsErr = s.cluster.Execute(er, addr, username, password, timeout)
+		if resultsErr.Error() == "Unauthorized" {
+			http.Error(w, ErrLeaderNotFound.Error(), http.StatusUnauthorized)
+			return
+		}
 		stats.Add(numRemoteExecutions, 1)
 		w.Header().Add(ServedByHTTPHeader, addr)
 	}