Collect Docker metrics with Prometheus

Summary:
Configure the Docker daemon as a Prometheus target.

With this change, daemon.json will now be always created.

Ref T1623

Test Plan:

• Deploy on Dwellers and docker-002
• curl 172.27.27.4:9323/metrics

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T1623

Differential Revision: https://devcentral.nasqueron.org/D3372