Changes callback on failed response decode in rpc service to pass act…

…ual error instead of 'error' string

src/rpc/service.js

@@ -118,7 +118,7 @@ Service.prototype.rpcCall = function rpcCall(method, requestCtor, responseCtor,
                         response = responseCtor[self.responseDelimited ? "decodeDelimited" : "decode"](response);
                     } catch (err) {
                         self.emit("error", err, method);
-                        return callback("error", err);
+                        return callback(err);
                     }
                 }