Fix memory leak in __virExec
Fix memory leak in __virExec

Commit e0d014f2379dd made binary potentially allocated on the heap.
It was freed in the parent in the error path, but not in the success path
that doesn't goto the cleanup label.

Found by 'make -C tests valgrind'.

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