Add auto restart plugin when containerd restart after

[lengrongfu]

Current containerd restart after the plugin will exit, I would like to add some code to the plugin as an example to show how to implement the auto restart plugin when containerd restart after

[klihub]

@lengrongfu Do you mean that you would like to see an example plugin (maybe the sample template plugin) showing how the plugin can reconnect when the runtime is shut down and restarted ?