docker compose外挂卷报Failed to locate volume for instance of deployment unit错误

https://github.com/rancher/rancher/issues/8497
如果要外挂卷对象有external: true，如下：

volumes:
  grafana-data:
    external: true
    driver: local
  prometheus-data:
    external: true
    driver: local

则需要先创建卷对象，否则会报Failed to locate volume for instance of deployment unit错误。
github的issue中建议先创建卷对象，或者将external: true去掉。