message: Update Docker APT references
  Docker repository address is changing in the end of March 2020. Also added current public key.
diff: #!/bin/sh
  +# Exit on error
  +set -e
  +
  # Add docker key and repository
  -apt-key adv --keyserver hkp://p80.pool.sks-keyservers.net:80 --recv-keys 58118E89F3A912897C070ADBF76221572C52609D
  -echo "deb https://apt.dockerproject.org/repo ubuntu-xenial main" | sudo tee /etc/apt/sources.list.d/docker.list
  +apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 9DC858229FC7DD38854AE2D88D81803C0EBFCD88
  +echo "deb [arch=amd64] https://download.docker.com/linux/ubuntu xenial stable" | sudo tee /etc/apt/sources.list.d/docker.list
  # Install apache and docker
  apt-get update -q
  apt-get upgrade -qy
  -apt-get install -qy apache2 docker-engine
  +apt-get install -qy apache2 docker-ce
  # Put the relevant files in place
  cp /tmp/juice-shop/default.conf /etc/apache2/sites-available/000-default.conf
  