[AWS] add describe_vpc_attribute
Denser code style
Merge pull request #2901 from goldendeal/describe_vpc_attribute

Add support for AWS describe_vpc_attribute
[aws|elb] Fix tests so that they work with FOG_MOCK=false for both EC2-Classic and VPC style AWS accounts.
[aws] update refs to ec2_compatibility_mode
Merge pull request #2893 from mikehale/fix-elb-tests

Fix elb tests