Fix aws-ec2 live tests

Still lots of problems, but the work so far is largely making security
group interactions use IDs rather than names everywhere in aws-ec2,
and moving EC2ApiMetadata and AWSEC2ApiMetadata to extend a common
BaseEC2ApiMetadata, but that seems to introduce further problems - see
AWSEC2TemplateBuilderLiveTest#testAssignability for an example of it failing.