spec: Fix undefined with_libnl
spec: Fix undefined with_libnl

When building libvirt RPM without macvtap, with_libnl would be
undefined.

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