tests: Clean up 'test_list'

tests: Clean up 'test_list'

* Make use of 'create_' helper functions
* Include every import on its own line
* Use underscore_case, rather than camelCase
* Don't use list comprehension without generating a list: use a for
  loop instead

Signed-off-by: Stephen Finucane <stephen.finucane@intel.com>
Reviewed-by: Andy Doan <andy.doan@linaro.org>