Use suggested json docker daemon config file

[manics]

See https://docs.docker.com/engine/reference/commandline/dockerd/#/linux-configuration-file

This should be used in the docker role, so the upstream docker.service systemd file can be used unmodified. This should avoid problems with breaking changes which would otherwise require a change to the template, e.g. https://github.com/openmicroscopy/infrastructure/pull/90