Correct permissions to /etc/keystone/domains

Set permission for /etc/keystone/domains/ directory to 0700 instead of
0600 which is required for Keystone to be able to list directory
contents.

Change-Id: I7536cc3f0bcbc8aea298ad76713e45cbb93a4b27
Closes-Bug: #1609319

ansible/roles/keystone/templates/keystone.json.j2

@@ -13,7 +13,7 @@
             "source": "{{ container_config_directory }}/domains",
             "dest": "/etc/keystone/domains",
             "owner": "keystone",
-            "perm": "0600",
+            "perm": "0700",
             "optional": true
         },
         {