qemu: setcpus: Report better errors
qemu: setcpus: Report better errors

Mention whether it was the live or persistent definition which caused an
error reported and explicitly error out in case when attempting to set
maximum vcpu count for a live domain.

andreabolognani/libvirt,eskultety/libvirt,taget/libvirt,fabianfreyer/libvirt,olafhering/libvirt,jardasgit/libvirt,datto/libvirt,VenkatDatta/libvirt,taget/libvirt,jardasgit/libvirt,zippy2/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,zippy2/libvirt,olafhering/libvirt,VenkatDatta/libvirt,zippy2/libvirt,VenkatDatta/libvirt,eskultety/libvirt,libvirt/libvirt,crobinso/libvirt,jfehlig/libvirt,taget/libvirt,andreabolognani/libvirt,nertpinx/libvirt,taget/libvirt,jfehlig/libvirt,eskultety/libvirt,eskultety/libvirt,eskultety/libvirt,andreabolognani/libvirt,nertpinx/libvirt,datto/libvirt,andreabolognani/libvirt,olafhering/libvirt,libvirt/libvirt,datto/libvirt,olafhering/libvirt,zippy2/libvirt,libvirt/libvirt,jardasgit/libvirt,nertpinx/libvirt,crobinso/libvirt,libvirt/libvirt,jardasgit/libvirt,jardasgit/libvirt,VenkatDatta/libvirt,fabianfreyer/libvirt,crobinso/libvirt,andreabolognani/libvirt,VenkatDatta/libvirt,datto/libvirt,jfehlig/libvirt,jfehlig/libvirt,taget/libvirt,nertpinx/libvirt,datto/libvirt,crobinso/libvirt,nertpinx/libvirt