test: use T.TempDir to create temporary test directory (#15400)

This commit replaces `ioutil.TempDir` with `t.TempDir` in tests. The
directory created by `t.TempDir` is automatically removed when the test
and all its subtests complete.

Prior to this commit, temporary directory created using `ioutil.TempDir`
needs to be removed manually by calling `os.RemoveAll`, which is omitted
in some tests. The error handling boilerplate e.g.
	defer func() {
		if err := os.RemoveAll(dir); err != nil {
			t.Fatal(err)
		}
	}
is also tedious, but `t.TempDir` handles this for us nicely.

Reference: https://pkg.go.dev/testing#T.TempDir

Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>

cmd/xl-storage_windows_test.go

@@ -24,8 +24,6 @@ import (
 	"bytes"
 	"context"
 	"fmt"
-	"io/ioutil"
-	"os"
 	"testing"
 )
 
@@ -42,16 +40,10 @@ func TestUNCPaths(t *testing.T) {
 		{string(bytes.Repeat([]byte("界"), 280)), false},
 		{`/p/q/r/s/t`, true},
 	}
-	dir, err := ioutil.TempDir("", "testdisk-")
-	if err != nil {
-		t.Fatal(err)
-	}
-	// Cleanup on exit of test
-	defer os.RemoveAll(dir)
+	dir := t.TempDir()
 
 	// Instantiate posix object to manage a disk
-	var fs StorageAPI
-	fs, err = newLocalXLStorage(dir)
+	fs, err := newLocalXLStorage(dir)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -81,15 +73,9 @@ func TestUNCPaths(t *testing.T) {
 // Test to validate xlStorage behavior on windows when a non-final path component is a file.
 func TestUNCPathENOTDIR(t *testing.T) {
 	// Instantiate posix object to manage a disk
-	dir, err := ioutil.TempDir("", "testdisk-")
-	if err != nil {
-		t.Fatal(err)
-	}
-	// Cleanup on exit of test
-	defer os.RemoveAll(dir)
+	dir := t.TempDir()
 
-	var fs StorageAPI
-	fs, err = newLocalXLStorage(dir)
+	fs, err := newLocalXLStorage(dir)
 	if err != nil {
 		t.Fatal(err)
 	}