##  How to regenerate cluster-agents.

kubectl patch clusters.management.cattle.io <REPLACE_WITH_CLUSTERID>--type=‘json’ -p=‘[{“op”: “replace”, “path”: “/status/apiEndpoint”,“” }, {“op”: “replace”, “path”: “/status/provider”,“”}, {“op”: “replace”, “path”: “/status/driver”,“” }]’ 

or 

kubectl patch clusters.management.cattle.io <REPLACE_WITH_CLUSTERID> -p '{"status":{"agentImage":"dummy"}}'

Also Check https://gist.github.com/superseb/076f20146e012f1d4e289f5bd1bd4971