[VTY] Remove OpenBSC specific node-exit handling from src/vty

The idea is to move the VTY code into libosmocore at some point,
and for that we need to eliminate OpenBSC specifics from it
diff --git a/openbsc/src/gprs/gprs_ns_vty.c b/openbsc/src/gprs/gprs_ns_vty.c
index 8f0628a..b18e651 100644
--- a/openbsc/src/gprs/gprs_ns_vty.c
+++ b/openbsc/src/gprs/gprs_ns_vty.c
@@ -37,6 +37,7 @@
 #include <openbsc/signal.h>
 #include <openbsc/gprs_ns.h>
 #include <openbsc/gprs_bssgp.h>
+#include <openbsc/vty.h>
 
 #include <vty/vty.h>
 #include <vty/command.h>
@@ -281,6 +282,7 @@
 	install_element(CONFIG_NODE, &cfg_ns_cmd);
 	install_node(&ns_node, config_write_ns);
 	install_default(NS_NODE);
+	install_element(NS_NODE, &ournode_exit_cmd);
 	install_element(NS_NODE, &cfg_nse_nsvci_cmd);
 	install_element(NS_NODE, &cfg_nse_remoteip_cmd);
 	install_element(NS_NODE, &cfg_nse_remoteport_cmd);