[libvirt] [PATCH 0/5] Refactoring of cgroups usage

Currently libvirtd creates its basic cgroup hierarchy when it starts up. This is bad because if people mount cgroups after libvirtd it is running it doesn't detect this. The second issue is that the driver code re-creates the virCgroupPtr instance for a domain over & over again, which is inefficient and bloats the code. Finally, if the driver is configured to only use a couple of the cgroups controllers, we are still creating the directories under all of them