cluster-api-provider-aws: Don't attempt to recreate an ELB after the cluster has been provisioned

/kind feature

Describe the solution you’d like [A clear and concise description of what you want to happen.]

If a cluster was created at time X, and then the user deletes the ELB , CAPA will try to recreate the ELB, which will have a new DNS endpoint which will not work. There’s not much point doing this, and CAPA also has issues updating the resource in Kubernetes because its own webhook rejects the update as immutable.

In this scenario, we should mark AWSCluster as failed, and inform the user the cluster is unrecoverable.

Long term, we should switch to using NLBs and a recoverable endpoint.

Anything else you would like to add: [Miscellaneous information that will assist in solving the issue.]

Environment:

• Cluster-api-provider-aws version:
• Kubernetes version: (use kubectl version):
• OS (e.g. from /etc/os-release):