Run end-to-end tests with Docker images

[joanlopez]

Problem

Recently we had to release a patch version (see v1.6.1) because during the release process, or even earlier in the SDLC, we didn't catch that Docker images stopped to automatically get chromium binary downloaded.

Proposal

We agreed during a recent squad sync meeting, in retrospective, that it would be good idea to run the existing end-to-end tests with Docker images. So, in cases like this, we could spot earlier any issues with the Docker images we build.