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

[Rajpratik71]

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 [email protected]

[abjyoti]

The build fails in CICD are due to older version of open-ness (20.12) used for build. The shell check errors reported there are resolved in openness 21.03 release. See if you can build this against 21.03 to overcome the CICD shell check errors blocking the merge.