r/grafana: Ensure configuration directory exists

The *grafana* package for Fedora creates `/etc/grafana`, but it is not
created by default on Buildroot-based systems.

roles/grafana/tasks/main.yml

@@ -5,6 +5,13 @@
   tags:
   - install
 
+- name: ensure grafana configuration directory exists
+  file:
+    path: /etc/grafana
+    mode: u=rwx,go=rx
+    owner: root
+    group: root
+    state: directory
 - name: ensure grafana is configured
   template:
     src: grafana.ini.j2