should we not treat the os image as a special artifact

[rcooke-warwick]

At the moment we include the OS image as a special artifact - specifying the path in the config.js. This image is stored in a specific location on the worker.

As a simplification step - what if the image was just included in the suite, along with the tests, and any other artifacts such as dockerfiles or bash scripts that are used in the tests?

[rcooke-warwick]

Having the image be seperate from the other test suite files (as is currently the case) has the following downsides:

• when writing tests, you might not know the path to the image you are manipulating/using
• many test cases might not even need an image to be sent - they instead rely on downloading one from the API. This means that a dummy image needs to be sent to avoid errors being thrown in the core
• a change to the code running on the testbot might cause existing tests to break, as the image locations are not know by the tests