Use Ubuntu 18.04 as base image for the official Docker image of GitLab Runner
Description
Currently 16.04 is used as Ubuntu base image.
1. Proposal
Update to Ubuntu 18.04.
2. Proposal
Use debian:stretch-slim
as base image to be more lightweight and profit from layer caching (most other images use Debian as base image).
Edited by Tomasz Maczukin