Regular Docker clean-up

[Bob H.]

Yesterday we had an ocp24 low disk space alert, while investigating I found that Docker had old, redundant container images dating back 9 months using most of the servers disk space.
To prevent this issue in the future we should configure the below command to run regularly on all Docker servers.

docker system prune -a -f 

The docs will also need updating as we will be automating this task: https://ocdsdeploy.readthedocs.io/en/latest/maintain/docker.html