etcd3/store: update creation test to use storage client

There is no functional difference between checking for an empty key
using the database client and doing so with the storage interface. Using
the latter allows this test to be more portable.

Signed-off-by: Steve Kuznetsov <skuznets@redhat.com>

staging/src/k8s.io/apiserver/pkg/storage/etcd3/store_test.go

@@ -115,16 +115,11 @@ func TestCreate(t *testing.T) {
 	obj := &example.Pod{ObjectMeta: metav1.ObjectMeta{Name: "foo", SelfLink: "testlink"}}
 
 	// verify that kv pair is empty before set
-	getResp, err := etcdClient.KV.Get(ctx, key)
-	if err != nil {
-		t.Fatalf("etcdClient.KV.Get failed: %v", err)
-	}
-	if len(getResp.Kvs) != 0 {
-		t.Fatalf("expecting empty result on key: %s", key)
+	if err := store.Get(ctx, key, storage.GetOptions{}, out); !storage.IsNotFound(err) {
+		t.Fatalf("expecting empty result on key %s, got %v", key, err)
 	}
 
-	err = store.Create(ctx, key, obj, out, 0)
-	if err != nil {
+	if err := store.Create(ctx, key, obj, out, 0); err != nil {
 		t.Fatalf("Set failed: %v", err)
 	}
 	// basic tests of the output