Allow users to configure insecure docker registries in the pipelines docker daemon.

Users would like the ability to configure insecure registries in the pipelines docker daemon.

https://docs.docker.com/registry/insecure/

Currently we dont allow users to configure the docker daemon due to security reasons.

However this setting is reasonable to allow users to configure.

We currently configure aspects of the docker daemon using environment variables we could allow users to add insecure registries via a similar mechanism.

#!yaml

pipelines:
  default:
    - step:
        services:
          - docker
        script:
          - docker system info

definitions:
  services:
    docker:
      environment:
        INSECURE_REGISTRIES: "http://registry:port"