Later, zip_to_dict calls ast.literal_eval which requires this be a
string.  We can remove this *and* the literal_eval call, however that
would require testing all the places we call these util functions.

It can now bring up instances as well as ASGs for a service.

Also update the VPC play to fix some bugs.
 - Add an EIP to the NAT.
 - Source/Dest checks need to be disabled for NAT instances.