zebra: fix infinite loop when deleting an interface

When deleting a VLAN interface after flushing its
addresses, zebra uses 100% CPU time and freezes.

 * interface.c: The while loop in line 407 that
   should clean up connected routes never hits one
   of the 2 lines "last = node;" and thus loops
   forever.

Signed-off-by: Roman Hoog Antink <rha@open.ch>

zebra/interface.c

@@ -477,6 +477,10 @@ if_delete_update (struct interface *ifp)
 		}
 	    }
 #endif /* HAVE_IPV6 */
+	  else
+	    {
+	      last = node;
+	    }
 	}
     }
   zebra_interface_delete_update (ifp);