Ansible 2.0 has deprecated the “ssh” from ansible_ssh_user, ansible_ssh_host, and ansible_ssh_port to become ansible_user, ansible_host, and ansible_port. If you are using a version of Ansible prior to 2.0, you should continue using the older style variables (ansible_ssh_*). These shorter variables are ignored, without warning, in older versions of Ansible.
I am not sure about the broader impact of this change. But I have seen on the requirements the version required is ansible>=2.4.0.
http://docs.ansible.com/ansible/latest/intro_inventory.html
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