This patch adds a libvirt hook that saves the VM console log everytime
it shutdown. This is great for troubleshooting because it allow us to
see what happened with the VM on every boot instead of only the last one.
Closes-Bug: #1506829
Related-Bug: #1393099
Change-Id: I4881dfc816a05c0fd2610b0b977e41c44a7e9517