fix the yaml formating, I suspect ansible became stricter on this this receently

Former-commit-id: 77819ea3

roles/mysql/tasks/mysql_server.yml

@@ -37,5 +37,5 @@
 
 - name: "Giving priviliges to user"
   mysql_user: name={{ mysql_user_name }} host={{ hostvars[item].ansible_fqdn }} password={{ mysql_user_password }} login_user=root login_password={{ mysql_root_password }} priv={{ mysql_user_db_name }}.*:ALL state=present
-  with_items: mysql_user_hosts_group
+  with_items: "{{ mysql_user_hosts_group }}"
   when: mysql_user_hosts_group is defined