ospfd: Tweak previous iface RR write patch to avoid free/malloc & redundant log

* linklist.{c,h}: (listnode_move_to_tail) new unction to move a
  listnode to tail of list.
* ospf_packet.c: (ospf_write) remove debug that seemed to be mostly covered
  by existing debug.
  Use listnode_move_to_tail to just move the list node to the end of the
  tail, rather than freeing the one to hand and allocing a new one.
diff --git a/lib/linklist.c b/lib/linklist.c
index 370b2fa..4b16f07 100644
--- a/lib/linklist.c
+++ b/lib/linklist.c
@@ -159,6 +159,13 @@
   list->count++;
 }
 
+/* Move given listnode to tail of the list */
+void
+listnode_move_to_tail (struct list *l, struct listnode *n)
+{
+  LISTNODE_DETACH(l,n);
+  LISTNODE_ATTACH(l,n);
+}
 
 /* Delete specific date pointer from the list. */
 void
diff --git a/lib/linklist.h b/lib/linklist.h
index 24a9e20..c8d715e 100644
--- a/lib/linklist.h
+++ b/lib/linklist.h
@@ -68,6 +68,7 @@
 extern void listnode_add (struct list *, void *);
 extern void listnode_add_sort (struct list *, void *);
 extern void listnode_add_after (struct list *, struct listnode *, void *);
+extern void listnode_move_to_tail (struct list *, struct listnode *);
 extern void listnode_delete (struct list *, void *);
 extern struct listnode *listnode_lookup (struct list *, void *);
 extern void *listnode_head (struct list *);