Add waiter when deleting objects to fix occasional flakiness (#3891)

Author: cenedhryn

services-custom/s3-transfer-manager/src/it/java/software/amazon/awssdk/transfer/s3/S3IntegrationTestBase.java

@@ -30,6 +30,7 @@
 import software.amazon.awssdk.services.s3.model.CreateBucketRequest;
 import software.amazon.awssdk.services.s3.model.DeleteBucketRequest;
 import software.amazon.awssdk.services.s3.model.DeleteObjectRequest;
+import software.amazon.awssdk.services.s3.model.HeadObjectRequest;
 import software.amazon.awssdk.services.s3.model.ListObjectVersionsRequest;
 import software.amazon.awssdk.services.s3.model.ListObjectVersionsResponse;
 import software.amazon.awssdk.services.s3.model.ListObjectsRequest;
@@ -141,6 +142,7 @@ protected static void deleteBucketAndAllContents(String bucketName) {
             }
             for (S3Object objectSummary : response.contents()) {
                 s3.deleteObject(DeleteObjectRequest.builder().bucket(bucketName).key(objectSummary.key()).build());
+                s3.waiter().waitUntilObjectNotExists(HeadObjectRequest.builder().bucket(bucketName).key(objectSummary.key()).build());
             }
 
             if (response.isTruncated()) {