Use secure persmissions for barbican configuration

This contains credentials, it shouldn't be world readable,
and certainly not writeable by the service user.

Change-Id: I165acd8c7568a80f463b32c73dd47102e10fdd07

tasks/barbican_post_install.yml

@@ -17,9 +17,9 @@
   config_template:
     src: "{{ item.source }}"
     dest: "{{ item.destination }}"
-    owner: "{{ barbican_system_user_name }}"
+    owner: "root"
     group: "{{ barbican_system_group_name }}"
-    mode: "0644"
+    mode: "0640"
     config_overrides: "{{ item.config_overrides }}"
     config_type: "{{ item.config_type }}"
   with_items: