Install docker in RPi jenkins dockerfile

[cgbahk]

Parents: https://github.com/cgbahk/backlog/issues/75

If you want to use e.g. Docker from your Jenkins CI system, you have multiple options:

• installing the Docker CLI using your base image’s packaging system (i.e. if your image is based on Debian, use .deb packages),
• using the Docker API.

Steps

• [x] docker ce requires Raspbian Stretch, but current dockerfile is jessie
• [x] follows official installation reference to install docker in docker
• [x] test whether jenkins actually can run docker and test in it

References:

• https://jpetazzo.github.io/2015/09/03/do-not-use-docker-in-docker-for-ci/
• https://getintodevops.com/blog/the-simple-way-to-run-docker-in-docker-for-ci
• https://docs.docker.com/install/linux/docker-ce/debian/

[cgbahk]

Following https://getintodevops.com/blog/the-simple-way-to-run-docker-in-docker-for-ci, it basically says to follow official installation guide..

[cgbahk]

Got to use 'convenience scripts' in https://get.docker.com for Raspbian. Looking good

Reference: https://docs.docker.com/install/linux/docker-ce/debian/#install-using-the-convenience-script

[cgbahk]

All done