Only log messages about updating root CA in CA server if it's the not the first time a cluster object has been set.
Only log messages about updating root CA in CA server if it's the
not the first time a cluster object has been set.

Signed-off-by: cyli <f39392f1e2d21dabc2bc5ab11d2bf832bde87b60@docker.com>

docker/swarmkit,RenaudWasTaken/swarmkit,jlhawn/swarmkit,dperny/swarmkit-1,RenaudWasTaken/swarmkit,diogomonica/swarmkit,sungwonh/swarmkit,dperny/swarmkit-1,diogomonica/swarmkit,sungwonh/swarmkit,docker/swarmkit,AliyunContainerService/swarmkit,alyyousuf7/swarmkit,Noyan759/swarmkit,cheyang/swarmkit,AliyunContainerService/swarmkit,Noyan759/swarmkit,cheyang/swarmkit,jlhawn/swarmkit,alyyousuf7/swarmkit