Switch from Dockerhub to Judock for CI pipeline

Dockerhub has limited the number of unauthenticated pulls per hour. We can switch the the Judock hosted by FZJ.

Documentation and configuration - https://itsdocs.app.fz-juelich.de/s/46bcf969-4408-40e1-95fd-6a9a3922f005/doc/judock-container-proxy-u58IxQ2pJ7#h-31-docker-engine-cli