Fixed firewall proposal when using VNC

- There was wrong firewall configuration file used for VNC case
- bnc#892899
Changes and version
Merge pull request #236 from kobliha/vnc-installation

Fixed firewall proposal in case of VNC installation
ifplugd package is not required. bnc#891517

ifplugd package is not present in SLE12. It was completely replaced by
wicked.
Updated testsuite for Lan::Packages
Lan::Packages - refactoring
Updated changelog