test/py: Import 'configparser' lower case to be python 3.x safe

In python 3.x the configparser module is named with all lower case.
Import it as such in order to avoid errors when running on python 3.x,
and fall back to the CamelCase version in order to keep working with
python 2.x.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>