Logging details regarding idle_time for Docker Autoscaler runners

Description

Currently, there seems to be no logging done for the "idle_time" field, for Gitlab runners setup using Docker Autoscaler as the executor.

The attached file contain the logs from /var/log/messages, from one of the runner manager instances. The idle_time configured (per config.toml file) is 3m30s. However, the runner log has no mention about the idle_time or about any instances identified to be terminated due to being idle.

Proposal

Make the log more verbose to also include details about idle_time.

Links to related issues and merge requests / references

• https://support.gitlab.com/hc/en-us/requests/610875