[feature request] yurtctl convert 支持重入

[hhstu]

What would you like to be added:

yurtctl convert 支持重入
Why is this needed:

按教程走的时候，第一波教程没有部署 yurt-tunnel，再次部署 yurtctl corcer yurt-tunnel时,会爆一些资源存在的错误

[root@RJYF-T-210 ~]# yurtctl convert --deploy-yurttunnel   --provider kubeadm   --cloud-nodes  rjyf-t-210
I1110 13:45:37.338948   30337 convert.go:325] mark rjyf-t-210 as the cloud-node
E1110 13:45:37.352020   30337 convert.go:337] fail to deploy yurtcontrollermanager: fail to create the serviceaccount/yurt-controller-manager: serviceaccounts "yurt-controller-manager" already exists
F1110 13:45:37.358914   30337 convert.go:105] fail to convert kubernetes to yurt: fail to create the serviceaccount/yurt-controller-manager: serviceaccounts "yurt-controller-manager" already exists

我觉得 资源存在时打个 warn 日志继续往下走会更好一些

others
/kind feature

[rambohe-ch]

@hhstu Very appreciate for your advice, I think it's convenient for end user when yurtctl covert can be idempotent.
Would you like to take over and add this feature for OpenYurt?

[rambohe-ch]

@adamzhoul Do you have any comments?

[adamzhoul]

agree

and @hhstu we have an #546 to use node-servant to convert the node which is idempotent
you should notice

and welcome you to take over the task, and make yurtctl convert idempotent

[hhstu]

@adamzhoul ok

[rambohe-ch]

@hhstu How about close this issue and assign issue #546 to you?