CLEANUP: server: Rename state_line node to node instead of name_name

<state_line.name_name> field is a node in an eb-tree. Thus, instead of
"name_name", we now use "node" to name this field. If is a more explicit
name and not too strange.

include/haproxy/server-t.h

@@ -377,8 +377,8 @@ struct server {
  */
 struct state_line {
 	char *line;
-	struct ebmb_node name_name;
-	/* WARNING don't put anything after name_name, it's used by the key */
+	struct ebmb_node node;
+	/* WARNING don't put anything after node, it's used by the key */
 };