runner: add a docker prune crojob
old images tend to pile up, so we need to schedule a garbage collection.

old images tend to pile up, so we need to schedule a garbage collection.
diff --git a/roles/gitlab-runner b/roles/gitlab-runner
Devan Carpenter b65f268a7f runner: add a docker prune crojob old images tend to pile up, so we need to schedule a garbage collection.		2 weeks ago
roles/gitlab-runner	runner: add a docker prune crojob	2 weeks ago
README.md	initialize: add gitlab-runner role	8 months ago
local.yml	initialize: add gitlab-runner role	8 months ago