Retire mount.Exec for k8s.io/utils/exec

This patch removes mount.Exec entirely and instead uses the common
utility from k8s.io/utils/exec.

The fake exec implementation found in k8s.io/utils/exec differs a bit
than mount.Exec, with the ability to pre-script expected calls to
Command.CombinedOutput(), so tests that previously relied on a callback
mechanism to produce specific output have been updated to use that
mechanism.

pkg/volume/azure_dd/azure_common_test.go

@@ -28,8 +28,7 @@ import (
 
 	"github.com/Azure/azure-sdk-for-go/services/compute/mgmt/2019-07-01/compute"
 	"github.com/stretchr/testify/assert"
-
-	"k8s.io/kubernetes/pkg/util/mount"
+	"k8s.io/utils/exec"
 )
 
 type fakeFileInfo struct {
@@ -126,7 +125,7 @@ func TestIoHandler(t *testing.T) {
 	if runtime.GOOS != "windows" && runtime.GOOS != "linux" {
 		t.Skipf("TestIoHandler not supported on GOOS=%s", runtime.GOOS)
 	}
-	disk, err := findDiskByLun(lun, &fakeIOHandler{}, mount.NewOSExec())
+	disk, err := findDiskByLun(lun, &fakeIOHandler{}, exec.New())
 	if runtime.GOOS == "windows" {
 		if err != nil {
 			t.Errorf("no data disk found: disk %v err %v", disk, err)