[FAB-16528] marbles private chaincode sync up

This CR is part 2 of porting changes in marbles
private in fabric/integration by FAB-15894 back
to fabric-samples

Signed-off-by: Dongming <dongming@ibm.com>
Change-Id: Ic823bdf4c3c571f43b4700452c50fd4283d35262

chaincode/marbles02_private/go/marbles_chaincode_private.go

@@ -523,18 +523,16 @@ func (t *SimpleChaincode) getMarblesByRange(stub shim.ChaincodeStubInterface, ar
 			return shim.Error(err.Error())
 		}
 		// Add a comma before array members, suppress it for the first array member
-		if bArrayMemberAlreadyWritten == true {
+		if bArrayMemberAlreadyWritten {
 			buffer.WriteString(",")
 		}
-		buffer.WriteString("{\"Key\":")
-		buffer.WriteString("\"")
-		buffer.WriteString(queryResponse.Key)
-		buffer.WriteString("\"")
 
-		buffer.WriteString(", \"Record\":")
-		// Record is a JSON object, so we write as-is
-		buffer.WriteString(string(queryResponse.Value))
-		buffer.WriteString("}")
+		buffer.WriteString(
+			fmt.Sprintf(
+				`{"Key":"%s", "Record":%s}`,
+				queryResponse.Key, queryResponse.Value,
+			),
+		)
 		bArrayMemberAlreadyWritten = true
 	}
 	buffer.WriteString("]")