qemu: Don't use -enable-nesting with qemu 1.2.0+
qemu: Don't use -enable-nesting with qemu 1.2.0+

Since the option doesn't exist. Fixes booting with
cpu mode='host-model' and qemu 1.2.0

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