cloud_aws: changes to enable deployment of on-spot instances (even with private ip address)

I managed to deploy 7 on spot instances with this (3 ebs backed, 4 ephemeral).

Problem with ephemeral backed on-spot instances is that they take _forever_ to get them running.

The default 300 seconds AWS_TIMEOUT is not enough for that.

Let me know if there is something you wish to have changed.