[aws|elb] add new style default security group

* AWS VPC enabled accounts have a new style security
  group separate from the 'amazon-elb-sg' group.
* added describe account attributes call
* use account attributes to determine elb security group
Merge pull request #2053 from engineyard/master

[aws|elb] add new style default security group
Merge pull request #2063 from maginatics/master

[google|compute] When 'insert'ing a disk, don't try to create an image.