ospfd: Make sure ospf_distribute_list_update_timer() eventually runs.

* ospf_zebra.c: (ospf_distribute_list_update_timer)
   If there are updates to the distribute list every 5 second or less,
   ospf_distribute_list_update_timer() will never run as the timer gets
   rearmed for each update. This fixes it by never rearming an active
   distribute list timer.

Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
diff --git a/ospfd/ospf_zebra.c b/ospfd/ospf_zebra.c
index 90bee21..462f67c 100644
--- a/ospfd/ospf_zebra.c
+++ b/ospfd/ospf_zebra.c
@@ -972,9 +972,9 @@
   if (!(rt = EXTERNAL_INFO (type)))
     return;
 
-  /* If exists previously invoked thread, then cancel it. */
+  /* If exists previously invoked thread, then let it continue. */
   if (ospf->t_distribute_update)
-    OSPF_TIMER_OFF (ospf->t_distribute_update);
+    return;
 
   /* Set timer. */
   ospf->t_distribute_update =