Use old name instead of hard coded 'precise64'
Fix hostname setting also in Debian

Same fix as #2334.
Merge pull request #2376 from tmatilai/debianoid-hostname

guests/debian: Fix fqdn/hostname setting on Debian and other that "precise64" Ubuntus
providers/virtualbox: Support VirtualBox 4.3 [GH-2374]
Update CHANGELOG