use n= in preferences file for distros that use a codename (take 4)

templates/etc/apt/preferences.d/sasl.erb

 <%-
   # Is @sasl_debian_distribution an "Archive" or "Codename"? If it's an Archive we
   # say
-  #    Pin: release a=<%= @sasl_debian_distribution %>
+  #    Pin: release a=archive-name
   #
   # If it's a Codename we way
   #
-  #    Pin: release n=<%= @sasl_debian_distribution %>
+  #    Pin: release n=code-name
   #
   # (See the apt_preferences man page for more information.)
   #
@@ -27,7 +27,6 @@
      'testing'
   ]
 
-  darg = 'n'
   if (archives.include?(@sasl_debian_distribution)) then
     darg = 'a'
   else