Ansible 2.5.1 breakage when generating image whitelist

After 2.5.1 update, Ansible is mishandling the docker_image_whitelist in genconfig when trying to add the xos_services array. It replaces the last item of the list over and over, instead of appending to the list, as was previous behavior:

This seems to be the problematic code:

https://github.com/opencord/cord/blob/master/ansible/roles/genconfig/tasks/main.yml#L80-L84