- [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 (localMethodInvokerMap != null && localMethodInvokerMap.size() > 0) {
            String methodName = RpcUtils.getMethodName(invocation);
            invokers = localMethodInvokerMap.get(methodName);
            if (invokers == null) {
                invokers = localMethodInvokerMap.get(Constants.ANY_VALUE);
            }
            if (invokers == null) {
                Iterator<List<Invoker<T>>> iterator = localMethodInvokerMap.values().iterator();
                if (iterator.hasNext()) {
                    invokers = iterator.next();
                }
            }
        }*/
        return invokers == null ? Collections.emptyList() : invokers;
    }
    @Override
    public Class<T> getInterface() {
        return serviceType;
    }
    @Override
    public URL getUrl() {
        return this.overrideDirectoryUrl;
    }
    @Override
    public boolean isAvailable() {
        if (isDestroyed()) {
            return false;
        }
        Map<String, Invoker<T>> localUrlInvokerMap = urlInvokerMap;
        if (localUrlInvokerMap != null && localUrlInvokerMap.size() > 0) {