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/data-update-tracker_test.go

@@ -21,7 +21,6 @@ import (
 	"bytes"
 	"context"
 	"fmt"
-	"io/ioutil"
 	"math/rand"
 	"os"
 	"path"
@@ -100,15 +99,11 @@ func TestDataUpdateTracker(t *testing.T) {
 
 	dut.Current.bf = dut.newBloomFilter()
 
-	tmpDir, err := ioutil.TempDir("", "TestDataUpdateTracker")
+	tmpDir := t.TempDir()
+	err := os.MkdirAll(filepath.Dir(filepath.Join(tmpDir, dataUpdateTrackerFilename)), os.ModePerm)
 	if err != nil {
 		t.Fatal(err)
 	}
-	err = os.MkdirAll(filepath.Dir(filepath.Join(tmpDir, dataUpdateTrackerFilename)), os.ModePerm)
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer os.RemoveAll(tmpDir)
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
 	dut.start(ctx, tmpDir)