Several updates to locations.ini.EC2-sample

- using AWS naming convetion for locations (e.g. us-east-1 instead of US_E)
- added Sydney location
- Updated AMI information with info from https://sites.google.com/a/webpagetest.org/docs/private-instances
Merge pull request #321 from gburiola/master

Several updates to locations.ini.EC2-sample