Call virsh undefine with --managed-save

Undefining a VM can fail if it has a managed save file, which then
triggers the debug messages of 'seed VM not running', 'seed VM not
defined', and then an error from libvirt that the domain exists. Also do
so in cleanup-env, to make sure the VMs die.

Change-Id: I51709f90f278d942bf37f2a8c4d725070ca54ac1
Merge "Call virsh undefine with --managed-save"