App image may not be found

[jschementi]

When running riker deploy, it's possible that the app AMI will not be found when actually deploying it, even though it's been created properly.

[jschementi]

This is because the AWS API just doesn't return it yet. A subsequent run of riker deploy-ami will find the AMI and deploy it.

Fix is to keep trying (for a fixed amount of time) to find the AMI.