virsh: Fix vol-name and vol-pool commands
virsh: Fix vol-name and vol-pool commands

This commands don't have a --pool option, so don't tell
vshCommandOptVolBy that there could be one. This made
vshCommandOptString for pooloptname fail and an "missing option"
error was reported.

Make pooloptname optional for vshCommandOptVolBy.

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