Unify testutil.Unmount on Windows and Unix

Signed-off-by: Paul "TBBle" Hampson <Paul.Hampson@Pobox.com>

pkg/testutil/helpers_unix.go

@@ -23,17 +23,9 @@ import (
 	"os"
 	"testing"
 
-	"github.com/containerd/containerd/mount"
 	"github.com/stretchr/testify/assert"
 )
 
-// Unmount unmounts a given mountPoint and sets t.Error if it fails
-func Unmount(t testing.TB, mountPoint string) {
-	t.Log("unmount", mountPoint)
-	err := mount.UnmountAll(mountPoint, umountflags)
-	assert.NoError(t, err)
-}
-
 // RequiresRoot skips tests that require root, unless the test.root flag has
 // been set
 func RequiresRoot(t testing.TB) {