s3api: fix bucket-root listing w/ delimiter (#7827)

* s3api: fix bucket-root listing w/ delimiter

* test: improve mock robustness for bucket-root listing test

- Make testListEntriesStream implement interface explicitly without embedding
- Add prefix filtering logic to testFilerClient to simulate real filer behavior
- Special-case prefix='/' to not filter for bucket root compatibility
- Add required imports for metadata and strings packages

This addresses review comments about test mock brittleness and accuracy.

* test: add clarifying comment for mock filtering behavior

Add detailed comment explaining which ListEntriesRequest parameters
are implemented (Prefix) vs ignored (Limit, StartFromFileName, etc.)
in the test mock to improve code documentation and future maintenance.

* logging

* less logs

* less check if already locked

weed/s3api/s3api_object_handlers_put.go

@@ -76,7 +76,7 @@ func (s3a *S3ApiServer) PutObjectHandler(w http.ResponseWriter, r *http.Request)
 	// http://docs.aws.amazon.com/AmazonS3/latest/dev/UploadingObjects.html
 
 	bucket, object := s3_constants.GetBucketAndObject(r)
-	glog.V(3).Infof("PutObjectHandler %s %s", bucket, object)
+	glog.V(2).Infof("PutObjectHandler bucket=%s object=%s size=%d", bucket, object, r.ContentLength)
 
 	_, err := validateContentMd5(r.Header)
 	if err != nil {