Connect already in progress,

- [x] Bug exists Release Version 1.2.5 ( Master Branch)
- [x] Bug exists in MQTTv3 Client on Snapshot Version 1.2.6-SNAPSHOT (Develop Branch)
- [x] Bug exists in MQTTv5 Client on Snapshot Version 1.2.6-SNAPSHOT (Develop Branch)

Hi,we are using the Paho MQTT Java client analog pressure test, There is a certain probability when the client connects:Connect already in progress,

Here is My Code

public class Mqtt3Test {
public static void main(String[] args) {
Integer begin =0;
Integer end =10000;
String defaultServer ="127.0.0.1:1883";
try {
CountDownLatch latch = new CountDownLatch(1);
for (int i=begin;i (a java.util.TaskQueue)
at java.util.TimerThread.run(Timer.java:505)

"MQTT Call: 8000 " #24140 prio=5 os_prio=0 tid=0x00007f7e2c58a800 nid=0xb3f98 in Object.wait() [0x00007f78f50db000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
at java.lang.Object.wait(Object.java:502)
at org.eclipse.paho.client.mqttv3.internal.CommsCallback.run(CommsCallback.java:198)
- locked <0x00000000c4c04cc0> (a java.lang.Object)
at java.lang.Thread.run(Thread.java:748)

"MQTT Snd: 8000 " #24139 prio=5 os_prio=0 tid=0x00007f7e2c588800 nid=0xb3f97 in Object.wait() [0x00007f78f51dc000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
at java.lang.Object.wait(Object.java:502)
at org.eclipse.paho.client.mqttv3.internal.ClientState.get(ClientState.java:836)
- locked <0x00000000c4c04cf0> (a java.lang.Object)
at org.eclipse.paho.client.mqttv3.internal.CommsSender.run(CommsSender.java:151)
at java.lang.Thread.run(Thread.java:748)

"MQTT Rec: 8000 " #24138 prio=5 os_prio=0 tid=0x00007f7e2c586800 nid=0xb3f96 runnable [0x00007f78f52dd000]
java.lang.Thread.State: RUNNABLE
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
at java.net.SocketInputStream.read(SocketInputStream.java:171)
at java.net.SocketInputStream.read(SocketInputStream.java:141)
at java.net.SocketInputStream.read(SocketInputStream.java:224)
at java.io.DataInputStream.readByte(DataInputStream.java:265)
at org.eclipse.paho.client.mqttv3.internal.wire.MqttInputStream.readMqttWireMessage(MqttInputStream.java:92)
at org.eclipse.paho.client.mqttv3.internal.CommsReceiver.run(CommsReceiver.java:160)
at java.lang.Thread.run(Thread.java:748)

I hope you can help me solve this problem,thank