[COOK-4322]: Fix the default path for the sasl_passwd file

Signed-off-by: Sean OMeara <someara@opscode.com>

recipes/sasl_auth.rb

@@ -43,11 +43,11 @@ sasl_pkgs.each do |pkg|
 end
 
 execute 'postmap-sasl_passwd' do
-  command 'postmap /etc/postfix/sasl_passwd'
+  command "postmap #{node['postfix']['sasl_password_file']}"
   action :nothing
 end
 
-template '/etc/postfix/sasl_passwd' do
+template node['postfix']['sasl_password_file'] do
   source 'sasl_passwd.erb'
   owner 'root'
   group 'root'