added required missing field for common yaml fmt

lib/ansible/plugins/inventory/openshift.py

@@ -19,6 +19,10 @@ DOCUMENTATION = '''
       - Uses openshift.(yml|yaml) YAML configuration file to set parameter values.
 
     options:
+      plugin:
+        description: token that ensures this is a source file for the 'openshift' plugin.
+        required: True
+        choices: ['openshift']
       connections:
           description:
           - Optional list of cluster connection settings. If no connections are provided, the default