NAS-129054 / 24.10 / Fix permissions on files under data directory

[Qubad786]

Problem

The test_data_dir_perms of the early_settings integration test was failing because some files, including user-services.json, truenas-eula-pending, and dhparam.pem, do not have 0o600 permissions when created by middlewared.

Solution

Specify the permissions of these files to be 0o600 when they are created by middlewared.

P.S permission for dhparam are not fixed as they should be handled in another PR we have open