title: DynamoDBScanExpression withLimit returns more records than Limit
body: <p>Have to list all the records from a DynamoDB table, without any filter expression.
  I want to limit the number of records hence using DynamoDBScanExpression with setLimit.</p>
  
  <pre><code>DynamoDBScanExpression scanExpression = new DynamoDBScanExpression();
  ....
  // Set ExclusiveStartKey
  ....
  scanExpression.setLimit(10);
  </code></pre>
  
  <p>However, the scan operation returns more than 10 results always !!!!
  Is this the expected behaviour and if so how?</p>