add linux package test healthcheck

[mowies]

This PR

• fixes [gh-actions] make linux package installation tests resilient to container image failures #623
• adds healthcheck commands to make sure that the container is fully booted up before attempting to continue installing the linux package under test

[cwegener]

Somehow is missed that this is now in a new repo!

The change makes sense to me. It's exactly what I had in mind.
I like the explicit use of podman exec.
It is the better option as opposed to the second option that I had considered which was to configure a Startup Health Check script.

The only improvement I could think of would be to write a very short blurb as a comment above the podman exec that concisely summarizes the reason why the podman exec is there (i.e. basically a short one-line summary of my original lengthy description)

(The reason for leaving a comment in-line would be because of the overall obscure nature of what is happening end-to-end in these tests. And the comment should help people who might not immediately see that the step from podman run to install deb/rpm is a very brittle piece that can easily fail in non-obvious ways)

[mowies]

@cwegener thanks for the feedback! i added a comment now, makes sense to me :)