Wrapper script to run smoke tests on Clever prod servers

Simple shell wrapper scripts have been sitting on my computers for a long time, here is a version for both instances, with the credentials singled out as environment variables or user input.

This is to be run with the working copy updated to the relevant branch (default, stable or oldstable) for the target platform. Reasons:

• the functional tests have to be adapted upon minor GitLab version changes (not systematic, yet frequent enough)
• we might have different options to provide in the wrapper script itself depending on Heptapod specifics (native mode would be a prime example of that).

Note: at the time of deployment of Heptapod 0.30.0 on both platforms, the stable branch is outdated, and the default branch is for Heptapod 0.30.

I've hesitated a bit between one single script for foss.h.n and heptapod.host or two scripts, because there have been times in the past when there were more differences than the login sequence. With a Python script, we can manage such differences in the future anyway.

The reason to bite the bullet and make a full Python script is the usual one: as long as there is at least an argument, chances that someone would call it with --help are high.

A full pipeline would be a waste of resources with this, the only relevant part being only flake8 for the new script. [skip ci]