change set-context to use-context

set-context allows setting configuration within a provided context, to change contexts we need "use-context"

$ kubectl config
...
  set-context     Sets a context entry in kubeconfig
  use-context     Sets the current-context in a kubeconfig file

installer/roles/kubernetes/tasks/kubernetes_auth.yml

@@ -1,3 +1,3 @@
 ---
 - name: Set the Kubernetes Context
-  shell: "kubectl config set-context {{ kubernetes_context }}"
+  shell: "kubectl config use-context {{ kubernetes_context }}"