index_files to be defined at server level if specified in resource::vhost

This partially avoids pitfall #2 (http://wiki.nginx.org/Pitfalls)

manifests/resource/vhost.pp

@@ -230,7 +230,7 @@ define nginx::resource::vhost (
       fastcgi_script      => $fastcgi_script,
       try_files           => $try_files,
       www_root            => $www_root,
-      index_files         => $index_files,
+      index_files         => undef,
       location_custom_cfg => $location_custom_cfg,
       notify              => Class['nginx::service'],
     }

templates/vhost/vhost_header.erb

@@ -31,6 +31,9 @@ server {
        return 301 https://$host$request_uri;
   }
 <% end -%>
+<% if @index_files -%>
+    index <% @index_files.each do |i| %> <%= i %><% end %>;
+<% end -%>
 
   access_log            <%= @access_log_real %>;
   error_log             <%= @error_log_real %>;

templates/vhost/vhost_ssl_header.erb

@@ -20,6 +20,9 @@ server {
 <% if defined? @auth_basic_user_file -%>
   auth_basic_user_file      "<%= @auth_basic_user_file %>";
 <% end -%>
+<% if @index_files -%>
+    index <% @index_files.each do |i| %> <%= i %><% end %>;
+<% end -%>
 
   access_log            <%= @ssl_access_log %>;
   error_log             <%= @ssl_error_log %>;