improve(bakery) support for custom organization providing prebaked conductor images

[Voronenko]

ISSUE TYPE

• Feature Pull Request

Addresses proposal in #965

SUMMARY

Allows 3rd parties to prebake and push custom conductor images with bakery command

CONDUCTOR_PROVIDER=softasap  python bakery.py

Allows also setting optional conductor_provider: ORG to provide a hint from which organization (default ansible) prebaked conductor image should be pulled from

version: "2"
settings:
  conductor_base: alpine:3.5
  conductor_provider: softasap
  volumes:
   - temp-space:/tmp   # Used to copy static content between containers

services:

   api-alpine:
     from: python:3.6.3-alpine3.6
     container_name: api-alpine
     entrypoint: [/docker-entrypoint]
     roles:
       - {
           role: "softasap.sa-container-bootstrap",
           option_container_syslog_ng: false,
           option_container_sshd: false
         }
#       - {
#           role: "softasap.sa-nginx-container",
#           container_init: "phusion-init" # uses runit for services management and upstart.
#         }
#       - {
#           role: "../custom-roles/app-nginx-stub-deploy"
#         }
     expose:
       - '8000'
     volumes:
        - temp-space:/tmp   # Used to copy static content between containers
     environment:
        IN_DOCKER: "1"

volumes:
  temp-space:
    docker: {}

[Voronenko]

See #965

[Voronenko]

No access for releasing pipeline for a while.
Aim of this PR is to allow 3rd parties still using ansible-container to host updated conductor images on premise.