[S3] Close opened S3Object

S3Object opened in getS3ObjectAndMetadata() should be closed.

s3/src/main/java/com/yahoo/ycsb/db/S3Client.java

@@ -353,6 +353,7 @@ public class S3Client extends DB {
         int sizeOfFile = (int)objectAndMetadata.getValue().getContentLength();
         fieldCount = sizeOfFile/sizeArray;
         totalSize = sizeOfFile;
+        objectAndMetadata.getKey().close();
       } catch (Exception e){
         System.err.println("Not possible to get the object :"+key);
         e.printStackTrace();