Provision MediaWiki-Vagrant on Jessie hosts
Add support for provisioning MediaWiki-Vagrant on Debian Jessie Labs
instances using LXC 2 packages provided via jessie-backports.
Bug: T154340
Depends-on: I13f1989070e24127a75addeb538c2be58633dd2a
Change-Id: I9b6d53609f28f1f35622ff2a0688059ef4de067f