fix ConfigMap data with leading underscore (#44)

[felixscheinost]

I tried doing the least amount of changes to fix keys with leading underscore in ConfigMap data.

[adrian-gierakowski]

I believe attrs starting with _ are filtered due to some specific “special” attrs which are use throughout the module system. See: https://github.com/search?q=repo%3Ahall%2Fkubenix+._&type=code

It might be better to compile a list of these and only exclude this specific list (everywhere).