zdb shouldn't print the path of a znode at verbosity < 5
zdb shouldn't print the path of a znode at verbosity < 5. There are two reasons:
1) Finding a znode's path is slower than printing any other znode information at verbosity < 5.
2) On a corrupted pool like the one mentioned below, zdb will crash when it tries to determine the znode's path. But with this patch, zdb can still extract useful information from such pools.