fix(k3s_server): skip installation if k3s binary already exists

Primary and secondary install tasks now check k3s_status.stat.exists
so re-running the playbook is idempotent on already-provisioned nodes.

roles/k3s_server/tasks/main.yaml

@@ -16,14 +16,18 @@
 
 - name: Install primary k3s server
   include_tasks: primary_installation.yaml
-  when: inventory_hostname == groups['k3s_server'] | first
+  when:
+    - inventory_hostname == groups['k3s_server'] | first
+    - not k3s_status.stat.exists
 
 - name: Get token from primary k3s server
   include_tasks: pull_token.yaml
 
 - name: Install seconary k3s servers
   include_tasks: secondary_installation.yaml
-  when: inventory_hostname != groups['k3s_server'] | first
+  when:
+    - inventory_hostname != groups['k3s_server'] | first
+    - not k3s_status.stat.exists
 
 - name: Set kubeconfig on localhost
   include_tasks: create_kubeconfig.yaml