[product: zaphod][project: zaphod-v0.3]: No hardcoded info in test_download.py

SYNOPSIS
[modified]m42/test/test_gzdownload.py: Get all download info from config file.

DETAILS
This commit removes hardcoded download information from the
test_gzdownload.py script. The download URLs and cache locations
are specified in the config file. Only this file has to be changed
to run a test against a different download server.
[product: zaphod][project: zaphod-v0.3]:[bugfix]: Add missing import

SYNOPSIS
[modified]m42/test/test_download.py: Add missing import os statement.

DETAILS
The cleanup of files fails silently without this import as the call
to os.import is inside a try catch block that ignore exceptions.