Stability Tests Region Required Bug

Stability Tests requires the environment variable "Region" set to some value like us-west-2. This information is actually not used when running tests to position clusters or tasks as those use region from the test configuration.

This is a bug.

The aws-cli should use region from configuration, not the environment variable/aws cli settings

Start by locating the Stability Tests entry point and the AWS CLI region-resolution code. Reproduce the failure with Region unset and a region in the test configuration; done means the tests no longer require the Region environment variable and cluster or task placement still follows the test configuration.

Written by the indexing model from the issue text.