set storage class in FS mode (minio#5779)

This change sets the storage class of the object-info if a storage
class was specified during PUT. The server now replies with the
storage class which was set during uploading the object in FS mode.

Fixes minio#5777

cmd/fs-v1-metadata.go

@@ -166,10 +166,14 @@ func (m fsMetaV1) ToObjectInfo(bucket, object string, fi os.FileInfo) ObjectInfo
 		}
 	}
 
-	// Extract etag from metadata.
 	objInfo.ETag = extractETag(m.Meta)
 	objInfo.ContentType = m.Meta["content-type"]
 	objInfo.ContentEncoding = m.Meta["content-encoding"]
+	if storageClass, ok := m.Meta[amzStorageClass]; ok {
+		objInfo.StorageClass = storageClass
+	} else {
+		objInfo.StorageClass = globalMinioDefaultStorageClass
+	}
 
 	// etag/md5Sum has already been extracted. We need to
 	// remove to avoid it from appearing as part of