Improve CI readability by labelling script steps

# Describe the feature you'd like to have #

Currently the CI jobs that run in Jenkins for each PR list shell commands for steps that are executed. These commands can be labelled with a short and understandable comment.

See [containerized-tests](https://jenkins-ceph-csi.apps.ocp.ci.centos.org/blue/organizations/jenkins/containerized-tests/) as an example, and click on a job to check the different stages there.

# What is the value to the end user? (why is it a priority?) #

Developers will understand the CI jobs better.

# How will we know we have a good solution? (acceptance criteria) #

Looking at CI jobs in Jenkins will show useful comments in the top of the steps (new), with the commands when expanding the view (as currently done).

This improves the understandability of the `*.groovy` files in the [ci/centos branch](https://github.com/ceph/ceph-csi/tree/ci/centos).

# Additional context #

Idea comes from noobaa/noobaa-core#6259

Start by reviewing the *.groovy files in the ci/centos branch and compare their Jenkins presentation with the containerized-tests example. Identify the shell-command steps and update their labels so Jenkins shows useful comments while keeping commands available when a step is expanded; verify the result by inspecting CI jobs in Jenkins.

Written by the indexing model from the issue text.