awsutils: add copy_image wrapper

The copy_image wrapper includes an additional kwarg 'wait_for_copy' that
will wait for the copy operation to complete before returning.
awsutils: add copy_image_to_all_regions function

Useful for deploying AMIs to all regions.
node: don't force nfs version 3 - use OS default

This change uses the default NFS version on the given AMI. On Ubuntu
11.10+ this defaults to NFSv4. Versions prior set the default to NFSv3.