qemu: Split up vCPU hotplug and hotunplug
qemu: Split up vCPU hotplug and hotunplug

There's only very little common code among the two operations. Split the
functions so that the internals are easier to understand and refactor
later.

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