docker: Refactor daemon.json using directly from YAML to JSON

[zachelnet]

Refactor the generation of /etc/docker/daemon.json from a template approach to direct YAML-to-JSON conversion using Ansible functions.

[ghost]

I changed back to template and added following code:

{% if docker_default_ulimits is defined and docker_default_ulimits | length > 0 %}
    "default-ulimits": {
{% for ulimit_name, ulimit_values in docker_default_ulimits.items() %}
        "{{ ulimit_name }}": {
            "Name": "{{ ulimit_values.Name }}",
            "Soft": {{ ulimit_values.Soft }},
            "Hard": {{ ulimit_values.Hard }}
        }{% if not loop.last %},{% endif %}
{% endfor %}

    },
{% endif %}