TestBuildMultiStageParentConfig: remove unneeded sleep and ImageList call

The `time.Sleep()` and `apiclient.ImageList()` were added in d3cc071bb98669545,
but appear to be debugging-code and not needed for the test.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

integration/build/build_test.go

@@ -9,7 +9,6 @@ import (
 	"io/ioutil"
 	"strings"
 	"testing"
-	"time"
 
 	"github.com/docker/docker/api/types"
 	"github.com/docker/docker/api/types/filters"
@@ -169,12 +168,6 @@ func TestBuildMultiStageParentConfig(t *testing.T) {
 	resp.Body.Close()
 	assert.NilError(t, err)
 
-	time.Sleep(30 * time.Second)
-
-	imgs, err := apiclient.ImageList(ctx, types.ImageListOptions{})
-	assert.NilError(t, err)
-	t.Log(imgs)
-
 	image, _, err := apiclient.ImageInspectWithRaw(ctx, "build1")
 	assert.NilError(t, err)