message: Fix cleanup code in stream_multiplexing
diff: @@ -150,7 +150,7 @@ public:
  CAF_CHECK_EQUAL(incoming_.num_streams(), 0u);
  CAF_CHECK_EQUAL(outgoing_.num_streams(), 0u);
  CAF_CHECK(streams().empty());
  - remotes().empty();
  + remotes().clear();
  }
  strong_actor_ptr remote_stream_serv(const node_id& nid) override;
  