Use proper Docker prune to remove waste

Use the correct and supported docker command to remove
all the waste of past images and containers, instead of relying
on ad-hoc scripts to find out what's old and dangling.

Change-Id: I8a3c0bc3540caeb4de75812ef6d08410134402a2
1 file changed
tree: 67b02a0d77c78f323dff34814a73a3f1f03ca397
  1. jenkins/
  2. jenkins-docker/
  3. worker/
  4. .gitignore