The local_settings file should not be world readable

It might contain sensitive information and as such it's
readability should be restricted.

Change-Id: I9d5605b8e9959796de33fa6cb0d3963bbe3cc0bb
Closes-Bug: rhbz#1217089

manifests/init.pp

@@ -394,7 +394,9 @@ class horizon(
   }
 
   concat { $::horizon::params::config_file:
-    mode    => '0644',
+    mode    => '0640',
+    owner   => $::horizon::params::wsgi_user,
+    group   => $::horizon::params::wsgi_group,
     require => Package['horizon'],
   }
 

releasenotes/notes/local-settings-permissions-666e7cd5d55cf813.yaml

@@ -0,0 +1,4 @@
+---
+security:
+  - local_settings file is no longer world readable (from 644 to 640) as it may
+    contain sensitive information.