syscall: Revert "release a js.Func object in fsCall"

This reverts CL 217417 (commit 753d56d3642eb83848aa39e65982a9fc77e722d7).

This change was unintentionally submitted to master during the
Go 1.14 code freeze; it should be sent again for Go 1.15.

Change-Id: Ie790342f227ae3adfc5f9a90ce3abdc2c9be619b
Reviewed-on: https://go-review.googlesource.com/c/go/+/217721
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Carlos Amedee <carlos@golang.org>
diff --git a/src/syscall/fs_js.go b/src/syscall/fs_js.go
index c1cac97..16d9f58 100644
--- a/src/syscall/fs_js.go
+++ b/src/syscall/fs_js.go
@@ -495,7 +495,7 @@
 	}
 
 	c := make(chan callResult, 1)
-	f := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
+	jsFS.Call(name, append(args, js.FuncOf(func(this js.Value, args []js.Value) interface{} {
 		var res callResult
 
 		if len(args) >= 1 { // on Node.js 8, fs.utimes calls the callback without any arguments
@@ -511,9 +511,7 @@
 
 		c <- res
 		return nil
-	})
-	defer f.Release()
-	jsFS.Call(name, append(args, f)...)
+	}))...)
 	res := <-c
 	return res.val, res.err
 }