Hardcode AMI for us-east-2 and eu-west-3 regions for Cloud-Base
Fedmsg topic 'org.fedoraproject.prod.fedimg.image.upload'
doesn't have AMI information for these two regions. We have
made AMIs available for these regions. So, hardcode these AMIs
for F28 Cloud-Base
Signed-off-by: Sinny Kumari <sinny@redhat.com>