Docker Daemon about cluster-lab

[whatever4711]

@Govinda-Fichtner Just discussed with @firecyberice that we will open a PR to docker.

For all others confronted with this error while starting clusterlab on non Hypriot-OS devices, execute the following script as superuser before running clusterlab:

#!/bin/sh
echo "Creating default daemon.json"
cat << EOF > /etc/docker/daemon.json
{
    "hosts": ["fd://"]
}
EOF

echo "Overwriting systemd docker daemon startup"
mkdir -p /etc/systemd/system/docker.service.d
cat << EOF > /etc/systemd/system/docker.service.d/clusterlab.conf
[Service]
ExecStart=
ExecStart=/usr/bin/docker daemon
EOF

echo "Reloading systemd and restarting docker"
systemctl daemon-reload
systemctl restart docker

[Govinda-Fichtner]

@whatever4711 This hypriot/image-builder-rpi@3c0ad0a commit ensures that it will work with the latest image out of the box.

For the standalone use (e.g. installation via package) we still need to determine what the best way is to handle this...