Reduce the time taken by airgapped testing scripts from pulling the images to pushing them to the airgapped instance's registry

[NohaIhab]

Context

During airgapped testing, every time we bring up the lxc instance the steps for moving around the images from the host machine to the airgapped instance need to run. These steps are very time-consuming and should not run on rerunning the airgapped testing scripts (only the first run). A high-level suggestion is to create a storage volume that can store the images, and be independent from the lxc instance.

What needs to get done

1. Explore how to make the registry setup process less time-consuming
2. Refactor the testing scripts based on the exploration

Definition of Done

1. the registry setup process in the testing scripts is more time-efficient
2. the images tar is not tightly coupled to the lxc instance