Make log shorter on IOException. This is not an ordinary exception. Info level. Others will be fired under error log level

common/transport/mqtt/src/main/java/org/thingsboard/server/transport/mqtt/MqttTransportHandler.java

@@ -883,7 +883,16 @@ public class MqttTransportHandler extends ChannelInboundHandlerAdapter implement
 
     @Override
     public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
-        log.error("[{}] Unexpected Exception", sessionId, cause);
+        if (cause instanceof IOException) {
+            if (log.isInfoEnabled()) {
+                log.info("[{}][{}] IOException: {}", sessionId,
+                        Optional.ofNullable(this.deviceSessionCtx.getDeviceInfo()).map(TransportDeviceInfo::getDeviceName).orElse(""),
+                        cause.getMessage());
+            }
+        } else {
+            log.error("[{}] Unexpected Exception", sessionId, cause);
+        }
+
         ctx.close();
         if (cause instanceof OutOfMemoryError) {
             log.error("Received critical error. Going to shutdown the service.");