Do not fail on unrelated validation tasks when Grafana not enabled

roles/matrix-grafana/tasks/main.yml

@@ -3,7 +3,7 @@
     - always
 
 - import_tasks: "{{ role_path }}/tasks/validate_config.yml"
-  when: run_setup|bool
+  when: "run_setup|bool and matrix_grafana_enabled|bool"
   tags:
     - setup-all
     - setup-grafana