Fix error on pull hang in CI

Kill the underlying containerd after outputting error. Otherwise CI
hangs indefinitely and requires the CI infrastructure to kill the build
at the timeout expiration.

Signed-off-by: Wei Fu <fuweid89@gmail.com>
Signed-off-by: Phil Estes <estesp@linux.vnet.ibm.com>

client_test.go

@@ -129,10 +129,11 @@ func TestMain(m *testing.M) {
 	}).Info("running tests against containerd")
 
 	// pull a seed image
+	log.G(ctx).Info("start to pull seed image")
 	if _, err = client.Pull(ctx, testImage, WithPullUnpack); err != nil {
-		ctrd.Stop()
-		ctrd.Wait()
 		fmt.Fprintf(os.Stderr, "%s: %s\n", err, buf.String())
+		ctrd.Kill()
+		ctrd.Wait()
 		os.Exit(1)
 	}