Update the aws-iam-authenticator docs to be more clear for both new and existing clusters.
Update the aws-iam-authenticator docs to be more clear for both new and existing clusters.

aledbf/kops,robinpercy/kops,gambol99/kops,justinsb/kops,gambol99/kops,kubernetes/kops,kubernetes/kops,aledbf/kops,robinpercy/kops,robinpercy/kops,justinsb/kops,robinpercy/kops,gambol99/kops,kubernetes/kops,gambol99/kops,aledbf/kops,justinsb/kops,aledbf/kops