labs: remove Vagrant files

This patch removes the files used by Vagrant to use the labs scripts.

Vagrant support is currently broken. The most pressing issue is that
some OpenStack software needs the VM rebooted after the distro software
updates, but doing that with Vagrant would take an extra effort. Same
goes for adding snapshots.

The presence of Vagrant-specific files confused quite a few people who
gained the impression that it is a requirement when it has always been
an alternative to osbash.

If there is sufficient interest in Vagrant support, we can add it back
later.

Change-Id: I7edfac1bb7c657d30acda0605a078c39d5fa997a
Merge "labs: remove Vagrant files"