SLE12 support for SLE11-SP3 

- Added support for SLE12 products
- Tested in SLES11-SP3
- 2.17.7

Found and fixed some additional bugs:

- Write FTP firewall port config
- Install `nfs-kernel-server` package when NFS server is selected (missing in minimal system)
NTH: `log.warn "... something wrong with #{distro}?"`