org.apache.dubbo.remoting.exchange.support.DefaultFuture#closeChannel doesn't work as expected since the channel instances to be compared do not have correct equals() implementation:

```java
 public static void closeChannel(Channel channel) {
        for (Map.Entry<Long, Channel> entry : CHANNELS.entrySet()) {
            if (channel.equals(entry.getValue())) { // in netty4, channel is NettyChannel, but entry.getValue() is NettyClient, equals will return false.
                DefaultFuture future = getFuture(entry.getKey());
                if (future != null && !future.isDone()) {
                    Response disconnectResponse = new Response(future.getId());
                    disconnectResponse.setStatus(Response.CHANNEL_INACTIVE);
                    disconnectResponse.setErrorMessage("Channel " +
                            channel +
                            " is inactive. Directly return the unFinished request : " +
                            future.getRequest());
                    DefaultFuture.received(channel, disconnectResponse);
                }
            }
        }
    }
```

This is the root cause of issue 1 in  #1968.
}
            channel.close();
        } catch (Exception e) {
            logger.warn(e.getMessage(), e);
        }
    }
    @Override
    public boolean hasAttribute(String key) {
        return attributes.containsKey(key);
    }
    @Override
    public Object getAttribute(String key) {
        return attributes.get(key);
    }
    @Override
    public void setAttribute(String key, Object value) {
        if (value == null) { 
            attributes.remove(key);
        } else {
            attributes.put(key, value);
        }
    }
    @Override
    public void removeAttribute(String key) {
        attributes.remove(key);
    }
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;