Let libosmocore handle VTY parent node tracking

* is_config_node is deprecated, so don't set it
* go_parent_cb is only used if we want to do special stuff upon exiting
  a node, in osmo-sgsn and gtphub only osmo_ss7_vty_go_parent() needs to
  be called

Change-Id: I2008dd9026922d29ee703c59e70d3fecced0ee18
1 file changed