test: use T.TempDir to create temporary test directory

The directory created by `T.TempDir` is automatically removed when the
test and all its subtests complete.

Reference: https://pkg.go.dev/testing#T.TempDir
Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>

integration/client/daemon_config_linux_test.go

@@ -35,15 +35,7 @@ import (
 
 // TestDaemonRuntimeRoot ensures plugin.linux.runtime_root is not ignored
 func TestDaemonRuntimeRoot(t *testing.T) {
-	runtimeRoot, err := os.MkdirTemp("", "containerd-test-runtime-root")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer func() {
-		if err != nil {
-			os.RemoveAll(runtimeRoot)
-		}
-	}()
+	runtimeRoot := t.TempDir()
 	configTOML := `
 version = 2
 [plugins]