util: Fix error message in __virExec
util: Fix error message in __virExec

Remove superfluous ": %s" suffix from the error message.

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