Fix Docker installations

`pip` can’t be found, `python-pip` is probably not properly installed

installing `docker-compose` and `docker` from Ubuntu repositories
now available in Ubuntu 16.04 Xenial!

Image deleted as part of GitLab backup shrinking project.
Trying to rebuild the image for jobs which do not define an image to
run with
https://forum.duniter.org/t/migration-de-gitlab-doppler-vega/12459/54

Dockerfile

@@ -5,10 +5,6 @@ ENV DEBIAN_FRONTEND noninteractive
 
 RUN apt-get update; \
    apt-get install -y curl apt-transport-https ca-certificates; \
-   apt-key adv --keyserver hkp://p80.pool.sks-keyservers.net:80 --recv-keys 58118E89F3A912897C070ADBF76221572C52609D; \
-   echo "deb https://apt.dockerproject.org/repo ubuntu-xenial main" > /etc/apt/sources.list.d/docker.list; \
    apt-get update; \
-   apt-get install -y docker-engine python-pip git; \
+   apt-get install -y docker docker-compose git; \
    apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
-
-RUN  pip install docker-compose
\ No newline at end of file