Support HA control-plane IP/address

[msnelling]

When creating a multi-master HA install, the created kubeconfig file has the IP address of the primary master (the node where the --cluster flag was used in installing the agent).

Expected Behaviour

Provide an option to override the IP or FQDN of the load balanced contol-plane API that is written to the kubeconfig file.

Current Behaviour

When installing in cluster mode the address of the initial master node is written to the kubeconfig file.

Possible Solution

Add a --cluster-api-address to override the address written to the kubeconfig.

Your Environment

• What Kubernetes distribution are you using?

Client Version: version.Info{Major:"1", Minor:"21", GitVersion:"v1.21.0", GitCommit:"cb303e613a121a29364f75cc67d3d580833a7479", GitTreeState:"clean", BuildDate:"2021-04-08T21:16:14Z", GoVersion:"go1.16.3", Compiler:"gc", Platform:"darwin/amd64"}
Server Version: version.Info{Major:"1", Minor:"21", GitVersion:"v1.21.1+k3s1", GitCommit:"75dba57f9b1de3ec0403b148c52c348e1dee2a5e", GitTreeState:"clean", BuildDate:"2021-05-21T16:12:29Z", GoVersion:"go1.16.4", Compiler:"gc", Platform:"linux/amd64"}

• What OS or type or VM are you using for your cluster? Where is it hosted? (for k3sup install/join): VMware Photon OS 4.0 VMs running on ESXi 7.0.2
• Operating System and version (e.g. Linux, Windows, MacOS): macOS 11.3.1

Darwin #####.local 20.4.0 Darwin Kernel Version 20.4.0: Thu Apr 22 21:46:47 PDT 2021; root:xnu-7195.101.2~1/RELEASE_X86_64 x86_64

"Be part of the solution"

Subject to approval, are you willing to work on a Pull Request for this issue or feature request? No

Are you a GitHub Sponsor (Yes/No?)

No

[alexellis]

This is already available via --tls-san

[alexellis]

/lock