Bug#916256: gitlab-runner fails when it tries to pull docker image gitlab-runner-helper:11.2.0

[Dean Hamstead]

This is doomed to fail with the default logic for the helper_image 
default

Per 
https://docs.gitlab.com/runner/configuration/advanced-configuration.html#helper-image

and

https://docs.gitlab.com/runner/configuration/advanced-configuration.html#overriding-the-helper-image