chore : use --no-cache-dir flag to pip in dockerfiles to save space

[Rajpratik71]

What this PR does / why we need it:

using --no-cache-dir flag in pip install ,make sure downloaded packages by pip don't cached on system . This is a best practice which make sure to fetch from repo instead of using local cached one . Further , in case of Docker Containers , by restricting caching , we can reduce image size. In term of stats , it depends upon the number of python packages multiplied by their respective size . e.g for heavy packages with a lot of dependencies it reduce a lot by don't caching pip packages.

Further , more detail information can be found at

https://medium.com/sciforce/strategies-of-docker-images-optimization-2ca9cc5719b6

Signed-off-by: Pratik Raj rajpratik71@gmail.com

Checklist

• [ ] Does this PR have a corresponding GitHub issue?
• [ ] Have you included relevant README for the chaoslib/experiment with details?
• [ ] Have you added debug messages where necessary?
• [ ] Have you added task comments where necessary?
• [ ] Have you tested the changes for possible failure conditions?
• [ ] Have you provided the positive & negative test logs for the e2ebook execution?
• [ ] Does the e2ebook ensure idempotency of cluster state?, i.e., is cluster restored to original state?
• [ ] Have you used non-shell/command modules for Kubernetes tasks?
• [ ] Have you (jinja) templatized custom scripts that is run by the e2ebook, if any?
• [ ] Have you (jinja) templatized Kubernetes deployment manifests used by the e2ebook, if any?
• [ ] Have you reused/created util functions instead of repeating tasks in the e2ebook?
• [ ] Do the artifacts follow the appropriate directory structure?
• [ ] Have you isolated storage (eg: OpenEBS) specific implementations, checks?
• [ ] Have you isolated platform (eg: baremetal kubeadm/openshift/aws/gcloud) specific implementations, checks?
• [ ] Are the ansible facts well defined? Is the scope explicitly set for playbook & included utils?
• [ ] Have you ensured minimum/careful usage of shell utilities (awk, grep, sed, cut, xargs etc.,)?
• [ ] Can the limtusbook be executed both from within & outside a container (configurable paths, no hardcode)?
• [ ] Can you suggest the minimal resource requirements for the e2ebook execution?
• [ ] Does the e2ebook job artifact carry comments/default options/range for the ENV tunables?
• [ ] Has the e2ebooks been linted?

Special notes for your reviewer: