Demote "specialized_init_system" certification test from "essential" to "normal"

[martin-mat]

Specialized_init_system in my opinion does not deserve to be "essential" for following reasons:

• the main reason for having init system inside containers is handling signals and zombies. There are specialized tests already among essential tests for those so this one seem to be redundant. Additionally, specialized init system is just one of ways how to handle signals/zombies.

• there is no good universal check for a specialized init system in cnf-testsuite. Current implementation checks for use just of "tini", "dumb-init", "s6-vscan" which is limiting.

I propose to leave it among certification tests, but demote from "essential" to "normal".

[taylor]

☝🏻 👀 @tomkivlin @pensarguet @jeffsaelens @vukg @electrocucaracha @nickolaev @wavell @HashNuke @denverwilliams

[wvwatson]

You can still have zombies with one of the popular, proper init systems like dummy init, just fyi. So another redundant check for zones is warranted.

If you know of well known init systems, feel free to add them.

Outside of that, reducing the amount of tests for microservices this will make passing harder, not easier. This is because you'll have less 'chances' to prove your good microservice practices. For example, if we removed the test you would now have 17 chances to pass 10 tests instead of 18 chances.

This count of tests was done to capture the idea that what is a cloud native good practice, e.g a good microservice practice, is hazy.

Check
https://cloud.google.com/blog/topics/developers-practitioners/graceful-shutdowns-cloud-run-deep-dive

https://cloud.google.com/architecture/best-practices-for-building-containers

And https://ahmet.im/blog/minimal-init-process-for-containers/ for some background

[agentpoyo]

Outside of that, reducing the amount of tests for microservices this will make passing harder, not easier. This is because you'll have less 'chances' to prove your good microservice practices. For example, if we removed the test you would now have 17 chances to pass 10 tests instead of 18 chances.

Are we still requiring 10 tests to pass with the most recent addition of 'essential" tests? On a few tests, I was seeing Coredns CNF fail the cert when it passed 14 of 19 tests.