virsh: Improve error when trying to change vm's cpu count 0
virsh: Improve error when trying to change vm's cpu count 0

This patch adds a check for the count of processors the user requests
for the guest machine so that invalid values produce a more helpful
error message.

dumbbell/libvirt,datto/libvirt,novel/fbsd-libvirt,nertpinx/libvirt,agx/libvirt,eskultety/libvirt,jeckersb/libvirt,nertpinx/libvirt,novel/fbsd-libvirt,jfehlig/libvirt,crobinso/libvirt,shugaoye/libvirt,zippy2/libvirt,bjzhang/libvirt,elmarco/libvirt,libvirt/libvirt,andreabolognani/libvirt,shugaoye/libvirt,olafhering/libvirt,fabianfreyer/libvirt,elmarco/libvirt,VenkatDatta/libvirt,olafhering/libvirt,shugaoye/libvirt,agx/libvirt,nertpinx/libvirt,wiedi/libvirt,shugaoye/libvirt,emaste/libvirt,novel/fbsd-libvirt,siboulet/libvirt-openvz,iam-TJ/libvirt,trainstack/libvirt,zhlcindy/libvirt-1.1.4-maintain,jardasgit/libvirt,rmarwaha/libvirt1,rmarwaha/libvirt,trainstack/libvirt,novel/fbsd-libvirt,jeckersb/libvirt,zippy2/libvirt,crobinso/libvirt,VenkatDatta/libvirt,elmarco/libvirt,siboulet/libvirt-openvz,iam-TJ/libvirt,datto/libvirt,iam-TJ/libvirt,eskultety/libvirt,zippy2/libvirt,emaste/libvirt,jardasgit/libvirt,dumbbell/libvirt,emaste/libvirt,iam-TJ/libvirt,rlaager/libvirt,siboulet/libvirt-openvz,libvirt/libvirt,agx/libvirt,warewolf/libvirt,jardasgit/libvirt,cbosdo/libvirt,rlaager/libvirt,emaste/libvirt,warewolf/libvirt,wiedi/libvirt,jfehlig/libvirt,wiedi/libvirt,eskultety/libvirt,rlaager/libvirt,zippy2/libvirt,fabianfreyer/libvirt,wiedi/libvirt,bjzhang/libvirt,VenkatDatta/libvirt,novel/fbsd-libvirt,cbosdo/libvirt,bjzhang/libvirt,rmarwaha/libvirt1,warewolf/libvirt,novel/fbsd-libvirt,warewolf/libvirt,rmarwaha/libvirt,andreabolognani/libvirt,crobinso/libvirt,rlaager/libvirt,zhlcindy/libvirt-1.1.4-maintain,eskultety/libvirt,dumbbell/libvirt,jeckersb/libvirt,rmarwaha/libvirt,siboulet/libvirt-openvz,warewolf/libvirt,emaste/libvirt,fabianfreyer/libvirt,rlaager/libvirt,datto/libvirt,wiedi/libvirt,novel/fbsd-libvirt,wiedi/libvirt,warewolf/libvirt,andreabolognani/libvirt,cbosdo/libvirt,emaste/libvirt,nertpinx/libvirt,jeckersb/libvirt,libvirt/libvirt,trainstack/libvirt,dumbbell/libvirt,libvirt/libvirt,emaste/libvirt,trainstack/libvirt,rmarwaha/libvirt1,rmarwaha/libvirt1,VenkatDatta/libvirt,cbosdo/libvirt,iam-TJ/libvirt,jfehlig/libvirt,taget/libvirt,iam-TJ/libvirt,bjzhang/libvirt,trainstack/libvirt,trainstack/libvirt,shugaoye/libvirt,jardasgit/libvirt,agx/libvirt,VenkatDatta/libvirt,taget/libvirt,warewolf/libvirt,rmarwaha/libvirt,cbosdo/libvirt,siboulet/libvirt-openvz,zhlcindy/libvirt-1.1.4-maintain,rmarwaha/libvirt,dumbbell/libvirt,novel/fbsd-libvirt,elmarco/libvirt,zhlcindy/libvirt-1.1.4-maintain,rmarwaha/libvirt,iam-TJ/libvirt,andreabolognani/libvirt,rmarwaha/libvirt1,jeckersb/libvirt,taget/libvirt,wiedi/libvirt,nertpinx/libvirt,taget/libvirt,agx/libvirt,rmarwaha/libvirt1,crobinso/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,jeckersb/libvirt,olafhering/libvirt,datto/libvirt,fabianfreyer/libvirt,jfehlig/libvirt,datto/libvirt,trainstack/libvirt,jeckersb/libvirt,olafhering/libvirt,taget/libvirt,dumbbell/libvirt,eskultety/libvirt,elmarco/libvirt,jardasgit/libvirt,bjzhang/libvirt,zhlcindy/libvirt-1.1.4-maintain,novel/fbsd-libvirt