must clear the list of routing protocols

src/internet-stack/ipv4-l3-protocol.cc

@@ -163,6 +163,7 @@ Ipv4L3Protocol::DoDispose (void)
       interface->Dispose ();
     }
   m_interfaces.clear ();
+  m_routingProtocols.clear ();
   m_node = 0;
   m_staticRouting->Dispose ();
   m_staticRouting = 0;