Fix examples to use right class.

Author: shhovhan

examples/natv3/list_private_dnat_rules.py

@@ -19,5 +19,5 @@
 openstack.enable_logging(True)
 conn = openstack.connect(cloud="otc")
 
-for dnat_rule in conn.privatenat.private_dnat_rules():
+for dnat_rule in conn.natv3.private_dnat_rules():
     print(dnat_rule)