Update SessionStrategy.java (thulab#478)

Author: CritasWang

iotdb-2.0/src/main/java/cn/edu/tsinghua/iot/benchmark/iotdb200/DMLStrategy/SessionStrategy.java

@@ -141,7 +141,7 @@ private Tablet genTablet(IBatch batch) {
             schemaList,
             columnTypes,
             batch.getRecords().size() * config.getDEVICE_NUM_PER_WRITE());
-    Object[] values = tablet.values;
+    Object[] values = tablet.getValues();
     int stepOff = 0;
     batch.reset();
     // Convert multiple batches to tablets