MQTT: disable https hostname verification (#820)

After the bump of Paho from 1.2.0 to 1.2.1 the library enables the https
hostname verification.
This breaks compatibility with current consumers.
Connections cannot be established anymore.

We disable the https hostname verification to keep the old behaviour.
We should add an API so the hostname verification can be enabled if
desired.

This also makes the version 1.2.1 the lower version limit as we need to
use the API to disable the verification internally.

Related to: https://github.com/openhab/openhab-core/issues/815

Signed-off-by: Markus Rathgeb <maggu2810@gmail.com>

bom/compile/pom.xml

@@ -206,7 +206,7 @@
     <dependency>
       <groupId>org.eclipse.paho</groupId>
       <artifactId>org.eclipse.paho.client.mqttv3</artifactId>
-      <version>1.2.0</version>
+      <version>1.2.1</version>
       <scope>compile</scope>
     </dependency>
 

bundles/org.openhab.core.io.transport.mqtt/src/main/java/org/eclipse/smarthome/io/transport/mqtt/MqttBrokerConnection.java

@@ -632,6 +632,7 @@ public class MqttBrokerConnection {
         }
 
         options.setKeepAliveInterval(keepAliveInterval);
+        options.setHttpsHostnameVerificationEnabled(false);
         return options;
     }