Failed resolution of: Ljavax/net/ssl/SNIHostName; on Android 6.0.1

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

```
java.lang.NoClassDefFoundError: Failed resolution of: Ljavax/net/ssl/SNIHostName;
at org.eclipse.paho.mqttv5.client.internal.SSLNetworkModule.start(SSLNetworkModule.java:135)
at org.eclipse.paho.mqttv5.client.internal.ClientComms$ConnectBG.run(ClientComms.java:783)
at java.lang.Thread.run(Thread.java:818)

Caused by: java.lang.ClassNotFoundException: Didn't find class "javax.net.ssl.SNIHostName" on path: DexPathList[[zip file "/data/app/com.yxggwzx.cashier-1/base.apk"],nativeLibraryDirectories=[/data/app/com.yxggwzx.cashier-1/lib/arm64, /data/app/com.yxggwzx.cashier-1/base.apk!/lib/arm64-v8a, /vendor/lib64, /system/lib64]]
at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)
at java.lang.ClassLoader.loadClass(ClassLoader.java:511)
at java.lang.ClassLoader.loadClass(ClassLoader.java:469)
at org.eclipse.paho.mqttv5.client.internal.SSLNetworkModule.start(SSLNetworkModule.java:135)
at org.eclipse.paho.mqttv5.client.internal.ClientComms$ConnectBG.run(ClientComms.java:783)
at java.lang.Thread.run(Thread.java:818)
```