Drop deprecated ioutil

`ioutil` has been deprecated by golang. All the code in `ioutil` just
forwards functionality to code in either the `io` or `os` packages.

See https://github.com/golang/go/pull/51961 for more info.

Signed-off-by: Jeff Widman <jeff@jeffwidman.com>

integration/client/export_test.go

@@ -19,7 +19,6 @@ package client
 import (
 	"archive/tar"
 	"io"
-	"io/ioutil"
 	"os"
 	"testing"
 
@@ -46,7 +45,7 @@ func TestExport(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	dstFile, err := ioutil.TempFile("", "export-import-test")
+	dstFile, err := os.CreateTemp("", "export-import-test")
 	if err != nil {
 		t.Fatal(err)
 	}

integration/client/import_test.go

@@ -21,7 +21,6 @@ import (
 	"context"
 	"encoding/json"
 	"io"
-	"io/ioutil"
 	"os"
 
 	"math/rand"
@@ -76,7 +75,7 @@ func testExportImport(t *testing.T, imageName string) {
 		t.Fatal(err)
 	}
 
-	dstFile, err := ioutil.TempFile("", "export-import-test")
+	dstFile, err := os.CreateTemp("", "export-import-test")
 	if err != nil {
 		t.Fatal(err)
 	}

integration/sandbox_clean_remove_windows_test.go

@@ -22,7 +22,7 @@ package integration
 import (
 	"encoding/json"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"net"
 	"os"
 	"os/exec"
@@ -75,7 +75,7 @@ func TestSandboxRemoveWithoutIPLeakage(t *testing.T) {
 		require.NoError(t, err)
 		defer f.Close()
 
-		data, err := ioutil.ReadAll(f)
+		data, err := io.ReadAll(f)
 		require.NoError(t, err)
 
 		var jsonData map[string]interface{}