Agent repeatedly logs <Response [400]> error message

Issues:
Fixes F5Networks#1315

Problem: Agent logs error when attempting to purge orphaned nodes.

Analysis: Orhpaned nodes are purged when pools are purged. Removed
call to separately purge nodes.

f5_openstack_agent/lbaasv2/drivers/bigip/agent_manager.py

@@ -810,7 +810,6 @@ def clean_orphaned_objects_and_save_device_config(self):
                 pools = self.lbdriver.get_all_deployed_pools()
                 if pools:
                     self.purge_orphaned_pools(pools)
-                    self.purge_orphaned_nodes(pools)
 
                 # Ask the BIG-IP for all deployed monitors not associated
                 # to a pool