Allow .htaccess with mod_rewrite for docs.openstack.org

Set AllowOverride to FileInfo so that .htaccess can use mod_rewrite
rules.
Also, turn rewrite engine on.

See http://httpd.apache.org/docs/current/mod/core.html#allowoverride

Change-Id: I94b3d936763acb9df5cb3ed43af2260c80dbb511

modules/openstack_project/templates/docs.vhost.erb

@@ -11,11 +11,15 @@ NameVirtualHost <%= @vhost_name %>:<%= @port %>
       <%= "  ServerAlias #{@serveraliases}" -%>
     <% end -%>
 
+    RewriteEngine on
+
     DocumentRoot <%= @docroot %>
     <Directory <%= @docroot %>>
         Options Indexes FollowSymLinks MultiViews
         Satisfy any
         Require all granted
+        # Allow mod_rewrite rules
+        AllowOverride FileInfo
     </Directory>
 
     ErrorLog /var/log/<%= scope.lookupvar("httpd::params::apache_name") %>/<%= @name %>_error.log