- [x] I have searched the [issues](https://github.com/apache/incubator-dubbo/issues) of this repository and believe that this is not a duplicate.
- [x] I have checked the [FAQ](https://github.com/apache/incubator-dubbo/blob/master/FAQ.md) of this repository and believe that this is not a duplicate.

### Environment

* Dubbo version: 2.7.0
* Operating System version: mac
* Java version: 1.8

### Steps to reproduce this issue

1.  `AbstractClient#initConnectStatusCheckCommand` set break point at `  !isConnected()`.
2. `AbstractClient#close()` set break point here.    
3.  start client first, start provider and then shutdown provider gracefully , let method `AbstractClient.close()` be executed. Then select step `1` and trigger the thread to execute `!isConnected`, here will always try to connect the offline machine.

Pls. provide [GitHub address] to reproduce this issue.

### Expected Result

What do you expected from the above steps？

When the server goes offline, the client will not reconnect the offline machine.

### Actual Result

What actually happens?

The client reconnects the offline machine every 2 seconds and causes a large number of arp packets(because ip is recycled and not available now).
if (!isConnected()) {
                            connect();
                        } else {
                            lastConnectedTime = System.currentTimeMillis();
                        }
                    } catch (Throwable t) {
                        String errorMsg = "client reconnect to " + getUrl().getAddress() + " find error . url: " + getUrl();
                        
                        if (System.currentTimeMillis() - lastConnectedTime > shutdown_timeout) {
                            if (!reconnect_error_log_flag.get()) {
                                reconnect_error_log_flag.set(true);
                                logger.error(errorMsg, t);
                                return;
                            }
                        }
                        if (reconnect_count.getAndIncrement() % reconnect_warning_period == 0) {
                            logger.warn(errorMsg, t);
                        }
                    }
                }
            };
            reconnectExecutorFuture = reconnectExecutorService.scheduleWithFixedDelay(connectStatusCheckCommand, reconnect, reconnect, TimeUnit.MILLISECONDS);
        }
    }
    private synchronized void destroyConnectStatusCheckCommand() {
        try {
            if (reconnectExecutorFuture != null && !reconnectExecutorFuture.isDone()) {
                reconnectExecutorFuture.cancel(true);
                reconnectExecutorService.purge();
            }