Warn if Docker daemon is out of space

[tstromberg]

We've noticed across a couple of friction logs that strange things occur when the Docker daemon is out of space, particularly with minikube.

Before calling docker build, could we check docker system df to make sure there is adequate space and emit a warning if not? This could also be useful as a trigger to prune images during startup (#4693).

NOTE: This would be applicable for both local builds (minikube docker-env) and remote builds.

[briandealwis]

I'm not sure docker system df provides information on free space:

$ docker system df --format '{{json .}}'
{"Active":"8","Reclaimable":"9.896GB (88%)","Size":"11.15GB","TotalCount":"61","Type":"Images"}
{"Active":"1","Reclaimable":"47.88MB (93%)","Size":"51.39MB","TotalCount":"19","Type":"Containers"}
{"Active":"5","Reclaimable":"535.4MB (3%)","Size":"14.73GB","TotalCount":"11","Type":"Local Volumes"}
{"Active":"0","Reclaimable":"1.136GB","Size":"1.136GB","TotalCount":"233","Type":"Build Cache"}