Too many connections / short SO_TIMEOUT / client disconnects often

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- [x] Bug exists Release Version 1.2.1 ( Master Branch)
- [x] Bug exists in MQTTv3 Client on Snapshot Version 1.2.1-SNAPSHOT (Develop Branch)
- [?] Bug exists in MQTTv5 Client on Snapshot Version 1.2.1-SNAPSHOT (Develop Branch)

Version 1.2.1 introduced this change:
https://github.com/eclipse/paho.mqtt.java/commit/d5379c3477119f9bdd59069271ddd21efb8c9628#diff-4facee5fd67e0fc8ce39f657db10c617
@rehanshaukat

This means WebSocketReceiver.java will get java.net.SocketTimeoutException when trying to read https://github.com/eclipse/paho.mqtt.java/blob/57c2c1e9830d8a8036bbb2513e22738c121a254f/org.eclipse.paho.client.mqttv3/src/main/java/org/eclipse/paho/client/mqttv3/internal/websocket/WebSocketReceiver.java#L103.

The exception will be caught later and the thread will be forced to stop:
https://github.com/eclipse/paho.mqtt.java/blob/57c2c1e9830d8a8036bbb2513e22738c121a254f/org.eclipse.paho.client.mqttv3/src/main/java/org/eclipse/paho/client/mqttv3/internal/websocket/WebSocketReceiver.java#L118

Because of that, the connection will often ends early, resulting with repeated connections attempts. And one client can create many more connection attempts than previous 1.2.0 version. The 1.2.1 puts much more pressure on the server-side. This can be reproduced with simple unit-test (pseudo-code):
```
MQTTClient client = new MQTTClient(WEBSOCKET_URI).connect().subscribe("topic");
assertTrue(client.isConnected());
Thread.sleep(10000);
assertTrue(client.isConnected()); // Fails in 1.2.1, works in 1.2.0
```

From the client perspective I'd like to have a way to provide custom SO_TIMEOUT. Another way to fix this could be to make SO_TIMEOUT longer, let's say same as connection timeout by default. Or maybe even socket read timeout exception should be treated differently.

Could you please review the code in the above links and discuss what's the proper solution should be?