tests: fix leaks in storagevolxml2argvtest
tests: fix leaks in storagevolxml2argvtest

Reported by John Ferlan.

olafhering/libvirt,shugaoye/libvirt,andreabolognani/libvirt,rlaager/libvirt,cbosdo/libvirt,agx/libvirt,olafhering/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,zippy2/libvirt,siboulet/libvirt-openvz,zippy2/libvirt,agx/libvirt,jfehlig/libvirt,elmarco/libvirt,fabianfreyer/libvirt,zhlcindy/libvirt-1.1.4-maintain,rlaager/libvirt,zhlcindy/libvirt-1.1.4-maintain,datto/libvirt,nertpinx/libvirt,shugaoye/libvirt,eskultety/libvirt,agx/libvirt,olafhering/libvirt,rlaager/libvirt,libvirt/libvirt,shugaoye/libvirt,nertpinx/libvirt,elmarco/libvirt,taget/libvirt,crobinso/libvirt,datto/libvirt,VenkatDatta/libvirt,zhlcindy/libvirt-1.1.4-maintain,rlaager/libvirt,nertpinx/libvirt,libvirt/libvirt,shugaoye/libvirt,datto/libvirt,crobinso/libvirt,crobinso/libvirt,eskultety/libvirt,siboulet/libvirt-openvz,crobinso/libvirt,jfehlig/libvirt,taget/libvirt,eskultety/libvirt,zhlcindy/libvirt-1.1.4-maintain,cbosdo/libvirt,nertpinx/libvirt,VenkatDatta/libvirt,libvirt/libvirt,jardasgit/libvirt,eskultety/libvirt,siboulet/libvirt-openvz,elmarco/libvirt,siboulet/libvirt-openvz,elmarco/libvirt,jardasgit/libvirt,VenkatDatta/libvirt,andreabolognani/libvirt,jardasgit/libvirt,datto/libvirt,siboulet/libvirt-openvz,jfehlig/libvirt,olafhering/libvirt,zippy2/libvirt,agx/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,cbosdo/libvirt,taget/libvirt,cbosdo/libvirt,zhlcindy/libvirt-1.1.4-maintain,jardasgit/libvirt,jfehlig/libvirt,zippy2/libvirt,shugaoye/libvirt,taget/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,libvirt/libvirt,andreabolognani/libvirt,cbosdo/libvirt,datto/libvirt,elmarco/libvirt,agx/libvirt,VenkatDatta/libvirt,jardasgit/libvirt,eskultety/libvirt,nertpinx/libvirt,rlaager/libvirt,VenkatDatta/libvirt,taget/libvirt