fs: use _final() for fs.WriteStream

use _final() method instead of once 'finish' event.
PR-URL: #20562
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: JacksonTian

lib/fs.js

@@ -2212,17 +2212,17 @@ function WriteStream(path, options) {
 
 if(typeofthis.fd!=='number')
 this.open();
-
-// dispose on finish.
-this.once('finish',function(){
-if(this.autoClose){
-this.destroy();
-}
-});
 }
 
 fs.FileWriteStream=fs.WriteStream;// support the legacy name
 
+WriteStream.prototype._final=function(callback){
+if(this.autoClose){
+this.destroy();
+}
+
+callback();
+};
 
 WriteStream.prototype.open=function(){
 fs.open(this.path,this.flags,this.mode,(er,fd)=>{