Verify VM has a serial port defined

[gdha]

See issue describing the problem with selinux and auto-relabeling: rear/rear-workshop-osbconf-2016#4
Comment from @N3WWN : VirtualBox defaults to not having a virtual serial port present on VMs. libvirt default to having a virtual serial port present on VMs

[gdha]

From @schlomo:
I reported this bug to CentOS as https://bugs.centos.org/view.php?id=13213 and I also created a Vagrantfile to show the problem and the fix at https://gist.github.com/schlomo/b532ba9bca87ea40d922d90e62b7338c

[schlomo]

IMHO we are chasing the wrong goal: Instead of fixing serial console in VirtualBox we should get rid of the requirement for it. Hence the bug report for CentOS.