cpuBaseline: Detect empty set of common features
cpuBaseline: Detect empty set of common features

In case the set of CPUs has no features in common, report incompatible
CPUs instead of returning the simplest CPU model with all features
disabled.

warewolf/libvirt,novel/fbsd-libvirt,bjzhang/libvirt,VenkatDatta/libvirt,shugaoye/libvirt,iam-TJ/libvirt,zippy2/libvirt,siboulet/libvirt-openvz,iam-TJ/libvirt,siboulet/libvirt-openvz,VenkatDatta/libvirt,trainstack/libvirt,bjzhang/libvirt,wiedi/libvirt,sshah-solarflare/Libvirt-PCI-passthrough-,iam-TJ/libvirt,danwent/libvirt-ovs,jeckersb/libvirt,wiedi/libvirt,leilihh/libvirt,iam-TJ/libvirt,leilihh/libvirt,jardasgit/libvirt,danwent/libvirt-ovs,emaste/libvirt,emaste/libvirt,eskultety/libvirt,trainstack/libvirt,rmarwaha/libvirt1,zippy2/libvirt,novel/fbsd-libvirt,fabianfreyer/libvirt,kantai/libvirt-vfork,cbosdo/libvirt,zippy2/libvirt,nertpinx/libvirt,amery/libvirt-vserver,rbu/libvirt,usc-isi/libvirt,jfehlig/libvirt,foomango/libvirt,warewolf/libvirt,emaste/libvirt,shugaoye/libvirt,novel/fbsd-libvirt,amery/libvirt-vserver,emaste/libvirt,iam-TJ/libvirt,zhlcindy/libvirt-1.1.4-maintain,kantai/libvirt-vfork,fabianfreyer/libvirt,datto/libvirt,andreabolognani/libvirt,elmarco/libvirt,agx/libvirt,warewolf/libvirt,shugaoye/libvirt,trainstack/libvirt,libvirt/libvirt,usc-isi/libvirt,rmarwaha/libvirt,datto/libvirt,rbu/libvirt,kantai/libvirt-vfork,kantai/libvirt-vfork,eskultety/libvirt,sshah-solarflare/Libvirt-PCI-passthrough-,datto/libvirt,taget/libvirt,kantai/libvirt-vfork,olafhering/libvirt,jardasgit/libvirt,rmarwaha/libvirt1,rlaager/libvirt,datto/libvirt,fabianfreyer/libvirt,novel/fbsd-libvirt,taget/libvirt,agx/libvirt,andreabolognani/libvirt,warewolf/libvirt,jeckersb/libvirt,soulxu/libvirt-xuhj,zhlcindy/libvirt-1.1.4-maintain,wiedi/libvirt,zhlcindy/libvirt-1.1.4-maintain,usc-isi/libvirt,jardasgit/libvirt,soulxu/libvirt-xuhj,novel/fbsd-libvirt,rlaager/libvirt,libvirt/libvirt,sshah-solarflare/Libvirt-PCI-passthrough-,trainstack/libvirt,foomango/libvirt,zhlcindy/libvirt-1.1.4-maintain,danwent/libvirt-ovs,iam-TJ/libvirt,warewolf/libvirt,rmarwaha/libvirt1,amery/libvirt-vserver,jeckersb/libvirt,soulxu/libvirt-xuhj,elmarco/libvirt,nertpinx/libvirt,zippy2/libvirt,jardasgit/libvirt,agx/libvirt,andreabolognani/libvirt,emaste/libvirt,rmarwaha/libvirt,siboulet/libvirt-openvz,dumbbell/libvirt,jfehlig/libvirt,cbosdo/libvirt,dumbbell/libvirt,jeckersb/libvirt,agx/libvirt,danwent/libvirt-ovs,jfehlig/libvirt,trainstack/libvirt,novel/fbsd-libvirt,taget/libvirt,dumbbell/libvirt,taget/libvirt,crobinso/libvirt,leilihh/libvirt,amery/libvirt-vserver,agx/libvirt,trainstack/libvirt,datto/libvirt,foomango/libvirt,bjzhang/libvirt,rmarwaha/libvirt,dumbbell/libvirt,rbu/libvirt,leilihh/libvirt,rmarwaha/libvirt,rlaager/libvirt,libvirt/libvirt,olafhering/libvirt,shugaoye/libvirt,iam-TJ/libvirt,siboulet/libvirt-openvz,libvirt/libvirt,zhlcindy/libvirt-1.1.4-maintain,rlaager/libvirt,novel/fbsd-libvirt,nertpinx/libvirt,wiedi/libvirt,soulxu/libvirt-xuhj,emaste/libvirt,warewolf/libvirt,rmarwaha/libvirt,VenkatDatta/libvirt,VenkatDatta/libvirt,eskultety/libvirt,cbosdo/libvirt,novel/fbsd-libvirt,olafhering/libvirt,jfehlig/libvirt,rlaager/libvirt,wiedi/libvirt,elmarco/libvirt,fabianfreyer/libvirt,jardasgit/libvirt,novel/fbsd-libvirt,rmarwaha/libvirt,wiedi/libvirt,bjzhang/libvirt,soulxu/libvirt-xuhj,sshah-solarflare/Libvirt-PCI-passthrough-,foomango/libvirt,warewolf/libvirt,danwent/libvirt-ovs,elmarco/libvirt,jeckersb/libvirt,rmarwaha/libvirt1,emaste/libvirt,VenkatDatta/libvirt,elmarco/libvirt,jeckersb/libvirt,crobinso/libvirt,andreabolognani/libvirt,dumbbell/libvirt,cbosdo/libvirt,bjzhang/libvirt,eskultety/libvirt,leilihh/libvirt,dumbbell/libvirt,wiedi/libvirt,trainstack/libvirt,cbosdo/libvirt,sshah-solarflare/Libvirt-PCI-passthrough-,rbu/libvirt,foomango/libvirt,rbu/libvirt,nertpinx/libvirt,rmarwaha/libvirt1,crobinso/libvirt,amery/libvirt-vserver,jeckersb/libvirt,rmarwaha/libvirt1,taget/libvirt,olafhering/libvirt,usc-isi/libvirt,eskultety/libvirt,andreabolognani/libvirt,nertpinx/libvirt,siboulet/libvirt-openvz,usc-isi/libvirt,crobinso/libvirt,shugaoye/libvirt,leilihh/libvirt,fabianfreyer/libvirt