Fix/cert write permission

[paolopoliti]

Description

This PR tackles an issue that prevents generation of X.509 certificate and private key during setup with Docker.

Checklist

• [] I have followed the indications in the CONTRIBUTING.
• [ ] The documentation related to the proposed change has been updated accordingly (plus comments in code).
• [ ] I have written new tests for my core changes, as applicable.
• [] I have successfully run tests with my changes locally.
• [] It is ready for review! :rocket: