Fix config.chunks processing during restore

For bigger files, config.chunks are just partially applied during the
selective restore. This fix applies to the whole config.chunks
collection's docs from the backup file.

Author: boris-ilijic

pbm/restore/selective.go

@@ -338,7 +338,11 @@ func (r *Restore) configsvrRestoreChunks(
 			models = append(models, mongo.NewInsertOneModel().SetDocument(doc))
 		}
 
-		if len(models) == 0 {
+		if len(models) == 0 && !done {
+			// if it's not done, we just reached maxBulkWriteCount, we need to process more
+			continue
+		} else if len(models) == 0 && done {
+			// it's done and there's nothing to update
 			return nil
 		}