qemu: cgroup: Setup only the top level disk image for read-write access
qemu: cgroup: Setup only the top level disk image for read-write access

Only the top level gets writes, so the rest of the backing chain
requires only read-only access.

zippy2/libvirt,jardasgit/libvirt,elmarco/libvirt,andreabolognani/libvirt,datto/libvirt,jfehlig/libvirt,rlaager/libvirt,nertpinx/libvirt,eskultety/libvirt,VenkatDatta/libvirt,agx/libvirt,shugaoye/libvirt,olafhering/libvirt,nertpinx/libvirt,rlaager/libvirt,taget/libvirt,crobinso/libvirt,olafhering/libvirt,zippy2/libvirt,agx/libvirt,libvirt/libvirt,andreabolognani/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,rlaager/libvirt,eskultety/libvirt,crobinso/libvirt,crobinso/libvirt,libvirt/libvirt,fabianfreyer/libvirt,datto/libvirt,fabianfreyer/libvirt,agx/libvirt,eskultety/libvirt,jardasgit/libvirt,shugaoye/libvirt,jfehlig/libvirt,shugaoye/libvirt,fabianfreyer/libvirt,olafhering/libvirt,libvirt/libvirt,VenkatDatta/libvirt,zippy2/libvirt,taget/libvirt,andreabolognani/libvirt,agx/libvirt,shugaoye/libvirt,elmarco/libvirt,rlaager/libvirt,andreabolognani/libvirt,shugaoye/libvirt,elmarco/libvirt,jfehlig/libvirt,nertpinx/libvirt,jardasgit/libvirt,elmarco/libvirt,olafhering/libvirt,agx/libvirt,libvirt/libvirt,datto/libvirt,rlaager/libvirt,VenkatDatta/libvirt,fabianfreyer/libvirt,zippy2/libvirt,taget/libvirt,eskultety/libvirt,jardasgit/libvirt,datto/libvirt,datto/libvirt,VenkatDatta/libvirt,elmarco/libvirt,jfehlig/libvirt,crobinso/libvirt,VenkatDatta/libvirt,taget/libvirt,jardasgit/libvirt,eskultety/libvirt,nertpinx/libvirt,taget/libvirt,nertpinx/libvirt