Shows commands on subfolders as well as the default topic (GoogleCloudPlatform#1467)

Author: gguuss

iot/mqtt_example/cloudiot_mqtt_example_nodejs.js

@@ -458,7 +458,7 @@ function mqttDeviceDemo(
  let messageStr = 'Message received: ';
  if (topic === `/devices/${deviceId}/config`) {
  messageStr = 'Config message received: ';
- } else if (topic === `/devices/${deviceId}/commands`) {
+ } else if (topic.startsWith(`/devices/${deviceId}/commands`)) {
  messageStr = 'Command message received: ';
  }