registry auth: fix check that node_oreg_auth_credentials_stat exists

roles/openshift_node/tasks/registry_auth.yml

@@ -56,4 +56,4 @@
     l_bind_docker_reg_auth: True
   when:
     - openshift_is_atomic | bool
-    - oreg_auth_user is defined or openshift_additional_registry_credentials != [] or node_oreg_auth_credentials_stat.stat.exists
+    - oreg_auth_user is defined or openshift_additional_registry_credentials != [] or ('stat' in node_oreg_auth_credentials_stat and node_oreg_auth_credentials_stat.stat.exists)