get_ami.py should now listen to fedimg.image.publish fedmsg
With fedimg 2.0.0, org.fedoraproject.prod.fedimg.image.publish
fedmsg topic is used to notify that AMIs are successfully
published to AWS EC2 regions. Fedmsg topic
org.fedoraproject.prod.fedimg.image.upload is sent only when
image gets successfully uploaded to base region.
Signed-off-by: Sinny Kumari <sinny@redhat.com>