packer: replace \r with literal on Ui for MR

packer/ui.go

@@ -270,6 +270,7 @@ func (u *MachineReadableUi) Machine(category string, args ...string) {
 	// Prepare the args
 	for i, v := range args {
 		args[i] = strings.Replace(v, ",", "%!(PACKER_COMMA)", -1)
+		args[i] = strings.Replace(args[i], "\r", "\\r", -1)
 		args[i] = strings.Replace(args[i], "\n", "\\n", -1)
 	}
 	argsString := strings.Join(args, ",")