Update apt cookbook

cookbooks/apt/recipes/unattended-upgrades.rb

@@ -1,8 +1,8 @@
 #
-# Cookbook Name:: apt
+# Cookbook:: apt
 # Recipe:: unattended-upgrades
 #
-# Copyright 2014, Chef Software, Inc.
+# Copyright:: 2014-2017, Chef Software, Inc.
 #
 # Licensed under the Apache License, Version 2.0 (the 'License');
 # you may not use this file except in compliance with the License.
@@ -29,19 +29,19 @@ package 'unattended-upgrades' do
 end
 
 package 'bsd-mailx' do
-  only_if { node['apt']['unattended_upgrades']['mail'] }
+  not_if { node['apt']['unattended_upgrades']['mail'].nil? }
 end
 
 template '/etc/apt/apt.conf.d/20auto-upgrades' do
   owner 'root'
   group 'root'
-  mode '644'
+  mode '0644'
   source '20auto-upgrades.erb'
 end
 
 template '/etc/apt/apt.conf.d/50unattended-upgrades' do
   owner 'root'
   group 'root'
-  mode '644'
+  mode '0644'
   source '50unattended-upgrades.erb'
 end