xinetd added to Vagrantfile and manage_dns set to 0

[JZfi]

The tftp service was not started automatically as the xinetd service was missing from Vagrantfile's provisioning. The dns is now disabled as the named service is not configured to be installed and will fail the cobbler sync task.

[thijsschnitger]

thanks for taking the time to improve this stuff! The DNS though is part of our usecase. IT would be better to add 'bind' to the yum lines in the vagrant file.