fs/zfs/zfs: Update dangling dn_new pointer in dnode_get_path()

fs/zfs/zfs: Update dangling dn_new pointer in dnode_get_path()

The dnode_get_path() traverses dnode structures to locate the dnode leaf
of a given path. When the leaf is a symlink to another path, it restarts
the traversal either from root or from a different path. In such cases,
dn_new must be re-initialized

Passes "make check".

Fixes: CID 86750
Signed-off-by: Jagannathan Raman <jag.raman@oracle.com>
Reviewed-by: Ross Philipson <ross.philipson@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>