nfs: support per-tx file accounting

rust/src/nfs/nfs.rs

@@ -587,6 +587,7 @@ impl NFSState {
         if let Some(NFSTransactionTypeData::FILE(ref mut d)) = tx.type_data {
             d.file_tracker.tx_id = tx.id - 1;
         }
+        tx.tx_data.init_files_opened();
         SCLogDebug!("new_file_tx: TX FILE created: ID {} NAME {}",
                 tx.id, String::from_utf8_lossy(file_name));
         self.transactions.push(tx);