Too many wp-cron requests even when disabled

We have a webserver with a number of WordPress instances. Most, if not all of them have disabled wp-cron.php using the wp-config.php line:

define('DISABLE_WP_CRON',true);

Despite this, there are more than a thousand requests a day that are made using wp-cron, and a typical logged request looks like this:

example.com:80 my.ip.add.res - - [19/Nov/2015:10:38:10 +0000] "POST /wp-cron.php?doing_wp_cron=1447929490.3804519176483154296875 HTTP/1.0" 404 36435 "-" "WordPress/3.9.6; http://example.com"

It’s a 404 request, because after trying really hard, I have deleted wp-cron.php from the folders. I know this is more of a server management question, but where does WordPress originate the wp-cron request from? Is there any part of the code that I could modify to ensure that this is never called?

Just felt it may help to add the entire config file (barring credentials) here
http://pastebin.com/4MMEw0fG

The cause is that the define in wp-config.php is below the line saying /* That's all, stop editing! Happy blogging. */

Anything defined below that is unlikely to have any impact on how wordpress works.