Re-enable CRIU tests by not using overlayfs snapshotter

While the issue hasn't been fixed in the kernel yet, we can workaround
the issue by not using overlayfs snapshotter.

The newly added step runs all tests that match /TestCheckpoint/.
So, TestCRWithImagePath has been renamed to match the regexp.

Fixes #3930.

Signed-off-by: Kazuyoshi Kato <katokazu@amazon.com>

integration/client/client_test.go

@@ -50,6 +50,7 @@ var (
 	noCriu            bool
 	supportsCriu      bool
 	testNamespace     = "testing"
+	testSnapshotter   = DefaultSnapshotter
 	ctrdStdioFilePath string
 
 	ctrd = &daemon{}
@@ -132,11 +133,30 @@ func TestMain(m *testing.M) {
 
 	// allow comparison with containerd under test
 	log.G(ctx).WithFields(logrus.Fields{
-		"version":  version.Version,
-		"revision": version.Revision,
-		"runtime":  os.Getenv("TEST_RUNTIME"),
+		"version":     version.Version,
+		"revision":    version.Revision,
+		"runtime":     os.Getenv("TEST_RUNTIME"),
+		"snapshotter": os.Getenv("TEST_SNAPSHOTTER"),
 	}).Info("running tests against containerd")
 
+	snapshotter := DefaultSnapshotter
+	if ss := os.Getenv("TEST_SNAPSHOTTER"); ss != "" {
+		snapshotter = ss
+	}
+
+	ns, ok := namespaces.Namespace(ctx)
+	if !ok {
+		fmt.Fprintln(os.Stderr, "error getting namespace")
+		os.Exit(1)
+	}
+	err = client.NamespaceService().SetLabel(ctx, ns, defaults.DefaultSnapshotterNSLabel, snapshotter)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "error setting %s's default snapshotter as %s: %s\n", ns, snapshotter, err)
+		os.Exit(1)
+	}
+
+	testSnapshotter = snapshotter
+
 	// pull a seed image
 	log.G(ctx).WithField("image", testImage).Info("start to pull seed image")
 	if _, err = client.Pull(ctx, testImage, WithPullUnpack); err != nil {
@@ -285,7 +305,7 @@ func TestImagePullWithDiscardContent(t *testing.T) {
 		t.Fatalf("there is no layers in the target image(parent: %v)", img.Target())
 	}
 	var (
-		sn    = client.SnapshotService("")
+		sn    = client.SnapshotService(testSnapshotter)
 		chain []digest.Digest
 	)
 	for i, dgst := range layers {