storage: Use virStoragePoolObjGetDef accessor for storage_util
storage: Use virStoragePoolObjGetDef accessor for storage_util

In preparation for privatizing the object, use the accessor.

Signed-off-by: John Ferlan <87558058f6f829e5ec976c8ef960720af4ff9c7d@redhat.com>

nertpinx/libvirt,olafhering/libvirt,crobinso/libvirt,crobinso/libvirt,nertpinx/libvirt,eskultety/libvirt,jardasgit/libvirt,andreabolognani/libvirt,jfehlig/libvirt,eskultety/libvirt,eskultety/libvirt,eskultety/libvirt,libvirt/libvirt,olafhering/libvirt,crobinso/libvirt,jardasgit/libvirt,jfehlig/libvirt,nertpinx/libvirt,libvirt/libvirt,jardasgit/libvirt,olafhering/libvirt,crobinso/libvirt,zippy2/libvirt,jfehlig/libvirt,olafhering/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,zippy2/libvirt,jardasgit/libvirt,jardasgit/libvirt,andreabolognani/libvirt,libvirt/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,jfehlig/libvirt,eskultety/libvirt,libvirt/libvirt,zippy2/libvirt,nertpinx/libvirt,nertpinx/libvirt,zippy2/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt