[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/gb_proxy_vty.c b/openbsc/src/gprs/gb_proxy_vty.c
index e1cf97e..babb089 100644
--- a/openbsc/src/gprs/gb_proxy_vty.c
+++ b/openbsc/src/gprs/gb_proxy_vty.c
@@ -29,6 +29,7 @@
 #include <openbsc/debug.h>
 #include <openbsc/gb_proxy.h>
 #include <openbsc/gprs_ns.h>
+#include <openbsc/vty.h>
 
 #include <vty/command.h>
 #include <vty/vty.h>
@@ -157,6 +158,7 @@
 	install_element(CONFIG_NODE, &cfg_gbproxy_cmd);
 	install_node(&gbproxy_node, config_write_gbproxy);
 	install_default(GBPROXY_NODE);
+	install_element(GBPROXY_NODE, &ournode_exit_cmd);
 	install_element(GBPROXY_NODE, &cfg_nsip_bss_local_ip_cmd);
 	install_element(GBPROXY_NODE, &cfg_nsip_bss_local_port_cmd);
 	install_element(GBPROXY_NODE, &cfg_nsip_sgsn_ip_cmd);