Fix compilation S3 repository

plugins/repository-s3/src/main/java/org/elasticsearch/repositories/s3/S3BlobContainer.java

@@ -32,6 +32,7 @@ import com.amazonaws.services.s3.model.ObjectMetadata;
 import com.amazonaws.services.s3.model.PartETag;
 import com.amazonaws.services.s3.model.PutObjectRequest;
 import com.amazonaws.services.s3.model.S3Object;
+import com.amazonaws.services.s3.model.S3ObjectSummary;
 import com.amazonaws.services.s3.model.UploadPartRequest;
 import com.amazonaws.services.s3.model.UploadPartResult;
 import org.apache.lucene.util.SetOnce;