qemu_hotplug: Resolve DEADCODE coverity error
qemu_hotplug: Resolve DEADCODE coverity error

Remove unused 'cgroup' variable in qemuDomainAttachDeviceDiskLive() to
resolve coverity DEADCODE complaint

agx/libvirt,eskultety/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,rlaager/libvirt,libvirt/libvirt,crobinso/libvirt,jfehlig/libvirt,rlaager/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,libvirt/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,fabianfreyer/libvirt,jfehlig/libvirt,jardasgit/libvirt,cbosdo/libvirt,andreabolognani/libvirt,olafhering/libvirt,agx/libvirt,taget/libvirt,eskultety/libvirt,VenkatDatta/libvirt,rlaager/libvirt,eskultety/libvirt,cbosdo/libvirt,VenkatDatta/libvirt,jardasgit/libvirt,olafhering/libvirt,agx/libvirt,cbosdo/libvirt,datto/libvirt,zippy2/libvirt,zhlcindy/libvirt-1.1.4-maintain,libvirt/libvirt,elmarco/libvirt,zhlcindy/libvirt-1.1.4-maintain,nertpinx/libvirt,zhlcindy/libvirt-1.1.4-maintain,rlaager/libvirt,taget/libvirt,andreabolognani/libvirt,VenkatDatta/libvirt,crobinso/libvirt,jfehlig/libvirt,nertpinx/libvirt,eskultety/libvirt,zhlcindy/libvirt-1.1.4-maintain,datto/libvirt,jfehlig/libvirt,eskultety/libvirt,shugaoye/libvirt,nertpinx/libvirt,nertpinx/libvirt,taget/libvirt,elmarco/libvirt,libvirt/libvirt,olafhering/libvirt,cbosdo/libvirt,zippy2/libvirt,elmarco/libvirt,andreabolognani/libvirt,datto/libvirt,VenkatDatta/libvirt,shugaoye/libvirt,crobinso/libvirt,taget/libvirt,elmarco/libvirt,shugaoye/libvirt,VenkatDatta/libvirt,jardasgit/libvirt,zhlcindy/libvirt-1.1.4-maintain,shugaoye/libvirt,datto/libvirt,taget/libvirt,agx/libvirt,agx/libvirt,shugaoye/libvirt,zippy2/libvirt,datto/libvirt,cbosdo/libvirt,olafhering/libvirt,crobinso/libvirt,andreabolognani/libvirt,zippy2/libvirt,fabianfreyer/libvirt,elmarco/libvirt,rlaager/libvirt