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

I really meant symbols instead of constants, since avoiding this usage of constants (as "labels") is one of the reasons for symbols to exist in Ruby.