storage: iscsi: Convert virExec to virCommand
storage: iscsi: Convert virExec to virCommand

v2:
    Use virCommand auto-cleanup

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