location suffix _wptdriver is automatically added.

Using the latest AMI (IE11/Chrome/Firefox/Safari (2014, wptdriver only) - ami-ecb3409b), If I send this on the user-data:
wpt_location=eu-west-1_wptdriver

Then I receive requests for:
GET /work/getwork.php?shards=1&location=eu-west-1_wptdriver_wptdriver