GCP: use YAML output

inventory/dynamic/gcp/ansible.cfg

@@ -28,6 +28,8 @@ inventory_ignore_extensions = secrets.py, .pyc, .cfg, .crt
 # work around privilege escalation timeouts in ansible:
 timeout = 30
 
+stdout_callback = yaml
+
 # Uncomment to use the provided example inventory
 inventory = hosts.sh