Use a DaemonSet instead of a Deployment to deploy our app

- For high availability reasons, we would like our app to scale linearly
  with the size of the control plane. Using a DaemonSet allows us to run
  one pod on each node-role.kubernetes.io/master node.
- The hope is that the Service that we create should load balance
  between these pods appropriately.

test/integration/app_availability_test.go

@@ -0,0 +1,33 @@
+/*
+Copyright 2020 VMware, Inc.
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package integration
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+
+	"github.com/suzerain-io/placeholder-name/test/library"
+)
+
+func TestAppAvailability(t *testing.T) {
+	library.SkipUnlessIntegration(t)
+	namespaceName := library.Getenv(t, "PLACEHOLDER_NAME_NAMESPACE")
+	daemonSetName := library.Getenv(t, "PLACEHOLDER_NAME_APP_NAME")
+
+	client := library.NewClientset(t)
+
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+
+	daemonSet, err := client.AppsV1().DaemonSets(namespaceName).Get(ctx, daemonSetName, metav1.GetOptions{})
+	require.NoError(t, err)
+
+	require.GreaterOrEqual(t, daemonSet.Status.NumberAvailable, int32(1))
+}