Downloading docker images with offline-installer's Python script:

python download.py --docker ../data_lists/onap_docker_images.list

does not work on Windows.

Scripts are usable also on Windows in case of using Minikube to host onap and when wanting to pre-download needed images for the setup.

Changing build/download/docker_downloader.py to connect docker engine in more default way i.e. taking engine parameters from environment fixes this script.