ansible/ansible — pull request #8353 by gdamjan (2014-07-30 13:20:22+00:00)
Title: return the most up-to-date info about an instance when starting/stopping it

otherwise the module will return the info about the instance that it got prior to the action taken
So if you had a task to start an instance:

ec2:
instance_ids: ...
state: running
register: ec2_info

the registered data would have empty public_dns_name, public_ip, private_dns_name, private_ip