[BUG] if clusterDefinition changes and takes affect cluster lifecycle, will lead to restart all related cluster.

[wangyelei]

In this scenario, how to update ClusterDefinition with user expectations。
For example,

1. the changes of CD will only be applied when the user triggers the opsRequest for cluster again, like vscale,restart,upgrade.
2. uses execute a corresponding command to apply these changes?

[shanshanying]

Maybe we can introduce a new policy for update, like what statefulset does spec.updateStrategy.