init: add missing O_CLOEXEC

    // Note in this case, that the source and destination directories are the same, so only one

    // fsync() is required.

    auto dir = Dirname(persistent_property_filename);

    auto dir_fd = unique_fd{open(dir.c_str(), O_DIRECTORY | O_RDONLY)};

    auto dir_fd = unique_fd{open(dir.c_str(), O_DIRECTORY | O_RDONLY | O_CLOEXEC)};

    if (dir_fd < 0) {

        return ErrnoError() << "Unable to open persistent properties directory for fsync()";

    }