bgpd: add useful notification logs (BZ#616)

* bgp_packet.c
  * bgp_notify_send_with_data(): add calls to zlog_info()
diff --git a/bgpd/bgp_packet.c b/bgpd/bgp_packet.c
index 1ed2328..5f15060 100644
--- a/bgpd/bgp_packet.c
+++ b/bgpd/bgp_packet.c
@@ -901,12 +901,25 @@
   if (sub_code != BGP_NOTIFY_CEASE_CONFIG_CHANGE)
     {
       if (sub_code == BGP_NOTIFY_CEASE_ADMIN_RESET)
-      peer->last_reset = PEER_DOWN_USER_RESET;
+      {
+        peer->last_reset = PEER_DOWN_USER_RESET;
+        zlog_info ("Notification sent to neighbor %s: User reset", peer->host);
+      }
       else if (sub_code == BGP_NOTIFY_CEASE_ADMIN_SHUTDOWN)
-      peer->last_reset = PEER_DOWN_USER_SHUTDOWN;
+      {
+        peer->last_reset = PEER_DOWN_USER_SHUTDOWN;
+        zlog_info ("Notification sent to neighbor %s: shutdown", peer->host);
+      }
       else
-      peer->last_reset = PEER_DOWN_NOTIFY_SEND;
+      {
+        peer->last_reset = PEER_DOWN_NOTIFY_SEND;
+        zlog_info ("Notification sent to neighbor %s: type %u/%u",
+                   peer->host, code, sub_code);
+      }
     }
+  else
+     zlog_info ("Notification sent to neighbor %s: configuration change",
+                peer->host);
 
   /* Call immediately. */
   BGP_WRITE_OFF (peer->t_write);