[cleanup] Make command nodes static

The cmd_nodes used to configure vty, can mostly be static so
(basic data hiding 101).
diff --git a/bgpd/bgp_dump.c b/bgpd/bgp_dump.c
index e815ea3..53dea80 100644
--- a/bgpd/bgp_dump.c
+++ b/bgpd/bgp_dump.c
@@ -773,7 +773,7 @@
 }
 
 /* BGP node structure. */
-struct cmd_node bgp_dump_node =
+static struct cmd_node bgp_dump_node =
 {
   DUMP_NODE,
   "",