ec2 endpoint configuration support
ec2 endpoint configuration support

- ec2.amazonaws.com / us-east-1 is the default ec2 endpoint;
  need to configure the appropriate endpoint when running elsewhere.

- aki id will also be different outside of us-east-1

Change-Id: Id5f58f553fb0bf9470ab822efc0e2890a5006a40

barthy1/bosh,barthy1/bosh,barthy1/bosh,barthy1/bosh