refactor: move from io/ioutil to io and os package

The io/ioutil package has been deprecated as of Go 1.16, see
https://golang.org/doc/go1.16#ioutil. This commit replaces the existing
io/ioutil functions with their new definitions in io and os packages.

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

mount/losetup_linux_test.go

@@ -17,7 +17,6 @@
 package mount
 
 import (
-	"io/ioutil"
 	"os"
 	"testing"
 
@@ -29,7 +28,7 @@ var randomData = []byte("randomdata")
 func createTempFile(t *testing.T) string {
 	t.Helper()
 
-	f, err := ioutil.TempFile("", "losetup")
+	f, err := os.CreateTemp("", "losetup")
 	if err != nil {
 		t.Fatal(err)
 	}