- [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).
} catch (Throwable e) {
            logger.warn(e.getMessage(), e);
        }
    }
    protected ExecutorService createExecutor() {
        return Executors.newCachedThreadPool(new NamedThreadFactory(CLIENT_THREAD_POOL_NAME + CLIENT_THREAD_POOL_ID.incrementAndGet() + "-" + getUrl().getAddress(), true));
    }
    public InetSocketAddress getConnectAddress() {
        return new InetSocketAddress(NetUtils.filterLocalHost(getUrl().getHost()), getUrl().getPort());
    }
    @Override
    public InetSocketAddress getRemoteAddress() {
        Channel channel = getChannel();
        if (channel == null) {
            return getUrl().toInetSocketAddress();
        }
        return channel.getRemoteAddress();
    }
    @Override
    public InetSocketAddress getLocalAddress() {
        Channel channel = getChannel();
        if (channel == null) {
            return InetSocketAddress.createUnresolved(NetUtils.getLocalHost(), 0);
        }
        return channel.getLocalAddress();
    }
    @Override
    public boolean isConnected() {
        Channel channel = getChannel();
        if (channel == null) {