Improving yamllint configuration (#11389)

Signed-off-by: Bas Meijer <bas.meijer@enexis.nl>

roles/etcd/tasks/install_docker.yml

@@ -28,7 +28,7 @@
     src: etcd.j2
     dest: "{{ bin_dir }}/etcd"
     owner: 'root'
-    mode: 0750
+    mode: "0750"
     backup: yes
   when: etcd_cluster_setup
 
@@ -37,6 +37,6 @@
     src: etcd-events.j2
     dest: "{{ bin_dir }}/etcd-events"
     owner: 'root'
-    mode: 0750
+    mode: "0750"
     backup: yes
   when: etcd_events_cluster_setup