Launch Instance seem to only validate ami-id with local list of ids making it impossible to launch EC2 images not returned from DC api

When I type in an instance ID on EC2 that is not part of the few DC returns (i.e. ami-7d07ec14) I'm told the image does not exist even though http://localhost:3001/api/images/ami-7d07ec14 says it does exist!

Seems like the check is only done against in memory loaded instances - that is not what should happen.

We need to fix this before B2 since its not usable with Ec2 without this.