azureblob,b2,s3: fix chunksize calculations producing too many parts

Before this fix, the chunksize calculator was using the previous size
of the object, not the new size of the object to calculate the chunk
sizes.

This meant that uploading a replacement object which needed a new
chunk size would fail, using too many parts.

This fix fixes the calculator to take the size explicitly.

backend/azureblob/azureblob.go

@@ -1678,14 +1678,14 @@ func (o *Object) Update(ctx context.Context, in io.Reader, src fs.ObjectInfo, op
 		}
 	}
 
-	uploadParts := int64(maxUploadParts)
+	uploadParts := maxUploadParts
 	if uploadParts < 1 {
 		uploadParts = 1
 	} else if uploadParts > maxUploadParts {
 		uploadParts = maxUploadParts
 	}
 	// calculate size of parts/blocks
-	partSize := chunksize.Calculator(o, int(uploadParts), o.fs.opt.ChunkSize)
+	partSize := chunksize.Calculator(o, src.Size(), uploadParts, o.fs.opt.ChunkSize)
 
 	putBlobOptions := azblob.UploadStreamToBlockBlobOptions{
 		BufferSize:      int(partSize),