[cleanup] Make command nodes static

The cmd_nodes used to configure vty, can mostly be static so
(basic data hiding 101).
diff --git a/ospfd/ospf_vty.c b/ospfd/ospf_vty.c
index c4abe7e..2e4b607 100644
--- a/ospfd/ospf_vty.c
+++ b/ospfd/ospf_vty.c
@@ -8073,7 +8073,7 @@
 
 
 /* ospfd's interface node. */
-struct cmd_node interface_node =
+static struct cmd_node interface_node =
 {
   INTERFACE_NODE,
   "%s(config-if)# ",
@@ -8184,13 +8184,6 @@
   install_element (INTERFACE_NODE, &no_ospf_transmit_delay_cmd);
 }
 
-/* Zebra node structure. */
-struct cmd_node zebra_node =
-{
-  ZEBRA_NODE,
-  "%s(config-router)#",
-};
-
 static void
 ospf_vty_zebra_init (void)
 {
@@ -8283,7 +8276,7 @@
 #endif /* 0 */
 }
 
-struct cmd_node ospf_node =
+static struct cmd_node ospf_node =
 {
   OSPF_NODE,
   "%s(config-router)# ",