Fixed selecting required packages (openssh, SuSEfirewall2) in case of default configuration + minimal sw selection

- Packages are now requested always
- Opens/closes ports as requested by user
- bnc#893126
- includes a little refactoring
- no test case, that require to put everything into lib/network (in TODO)
- tested in production

So, once this is implemented and we switch to raising exceptions (I'd suggest to do it after SLE 12, but still in SP1), then I can gladly replace this with symbols.