zclient: fix router-id calculation for IPv6 (#595)

If router-id is not specified in ospf6d.conf, ospf6d will get it from
the zebra daemon. But ospf6d originates Link LSAs before the router-id
is returned by zebra, thus this router's Link LSAs will be flooded
with AdvRouter set to 0.

* zclient.c: zclient_start(): send ZEBRA_INTERFACE_ADD message after
  ZEBRA_ROUTER_ID_ADD, not before
diff --git a/lib/zclient.c b/lib/zclient.c
index d3d5322..52a3627 100644
--- a/lib/zclient.c
+++ b/lib/zclient.c
@@ -339,12 +339,12 @@
   /* Create read thread. */
   zclient_event (ZCLIENT_READ, zclient);
 
-  /* We need interface information. */
-  zebra_message_send (zclient, ZEBRA_INTERFACE_ADD);
-
   /* We need router-id information. */
   zebra_message_send (zclient, ZEBRA_ROUTER_ID_ADD);
 
+  /* We need interface information. */
+  zebra_message_send (zclient, ZEBRA_INTERFACE_ADD);
+
   /* Flush all redistribute request. */
   for (i = 0; i < ZEBRA_ROUTE_MAX; i++)
     if (i != zclient->redist_default && zclient->redist[i])