Keep docker caches clean

[d-tork]

An enormous drain on storage is often dangling/unused docker images and volumes. To clear this out, use a variety of pruneing methods, but ultimately this was the only one that truly worked for me on Sizemore:

docker system prune -a

[d-tork]

One of the facts Ansible can check is free disk space on each partition. There should be a task or play that runs with a regular update playbook which, on the condition of having X% free space, cleans docker caches, apt cache, etc.