[cern] k8s_fedora: Add admin user
cherry-pick: https://review.openstack.org/#/c/563679/ jira: OS-6474
Add an admin service account and give it the cluster role. It can be used for access apps with token authentication like the kubernetes-dashboard.
Remove the cluster role from the dashboard service account.
Change-Id: I7980c0e72b0d71921e42af7338d02b8a1e563c34 Closes-Bug: #1766284 (cherry picked from commit 91d5229b)
Closes OS-6474