Investigate vagrant-lxc for our build system

It’s in Debian Stretch and could be an easier way to have something that works on our target platforms, including on our infrastructure (as opposed to vagrant-libvirt).

One challenge here is to avoid wasting too much dev+maintenance time on supporting both vagrant-libvirt and vagrant-lxc: that effort can easily cost more than the hardware that could simply use vagrant-libvirt (and nested KVM).

Parent Task: #5630 (closed)

Related issues

• Has duplicate #6787 (closed)

Original created by @intrigeri on 10232 (Redmine)