Update Dockerfile

[UnaffiliatedCode]

Added explicit permissions to the tests sub-folder since the folder hasn't been created when the image has been initialized. This can cause permission issues.

[ppodgorsek]

As mentioned in issue #381, the test folder is mounted when running the image. It is the responsibility of the process/thread starting the container to ensure the permissions are correct.

It is a bad practice to run containers as root, and this "fix" cannot work for non-root users.

Closing it as invalid.

[UnaffiliatedCode]

This proposal assigns permissions based on the configured environment variable as done with the 1000:1000 user, but also assigns (and creates the folder) for tests.

This has nothing to do with the Root user. This just explicitly extends the permissions to the configured tests sub-folder.

[ppodgorsek]

If the test folder belongs to a different user, this will fail, hence why only the root user could execute it in most situations.
It actually highlights a potential bug for the reports folder, where this is done too - this is a mistake. (new issue created to track that defect #403)