Support Ansible 2.4

[s01ipsist]

https://github.com/ansible/ansible/blob/devel/CHANGELOG.md#deprecated-modules-to-be-removed-in-28
ec2_facts has been deprecated and replaced by
https://docs.ansible.com/ansible/2.4/ec2_metadata_facts_module.html
but the outputs appear the same.

Could use
http://docs.ansible.com/ansible/latest/playbooks_variables.html#ansible-version
to switch based on running ansible version

Could also "not" call this module if ansible_ec2_placement_region is already defined although that might only work for people who have hardcoded regions.