Add busybox-statefulset application

Like the busybox deployment using 2 replicas and statefulset.

The application uses the same labels and names as the busybox
application to make it easy to test both applications. The only
difference is the namespace: "busybox-sample-statefulset" instead of
"busybox-sample". This way we can run both application in the same
cluster concurrently.

Issues:
- Need to improve directory layout
- Not tested yet
- Need to update README

Signed-off-by: Nir Soffer <nsoffer@redhat.com>

busybox-statefulset/kustomization.yaml

@@ -0,0 +1,5 @@
+---
+resources:
+- statefulset.yaml
+commonLabels:
+  appname: busybox

busybox-statefulset/statefulset.yaml

@@ -0,0 +1,48 @@
+---
+apiVersion: apps/v1
+kind: StatefulSet
+metadata:
+  name: busybox
+spec:
+  selector:
+    matchLabels:
+      appname: busybox
+  replicas: 2
+  template:
+    metadata:
+      labels:
+        appname: busybox
+    spec:
+      containers:
+        - name: logger
+          image: quay.io/nirsof/busybox:stable
+          imagePullPolicy: IfNotPresent
+          command:
+            - sh
+            - -c
+            - |
+              emit() {
+                  echo "$(date) $1" | tee -a /mnt/log/outfile
+                  sync /mnt/log/outfile
+              }
+              trap "emit STOP; exit" TERM
+              emit START
+              while true; do
+                  sleep 10 & wait
+                  emit UPDATE
+              done
+          volumeMounts:
+            - name: log
+              mountPath: /mnt/log
+  volumeClaimTemplates:
+    - metadata:
+        labels:
+          appname: busybox
+        name: busybox-pvc
+      spec:
+        accessModes:
+          - ReadWriteOnce
+        storageClassName: rook-ceph-block
+        resources:
+          requests:
+            storage: 1Gi

dr-statefulset/kustomization.yaml

@@ -0,0 +1,6 @@
+---
+resources:
+  - ../dr
+namespace: busybox-sample-statefulset
+commonLabels:
+  app: busybox-sample-statefulset

subscription-statefulset/kustomization.yaml

@@ -0,0 +1,14 @@
+---
+resources:
+  - ../subscription
+namespace: busybox-sample-statefulset
+commonLabels:
+  app: busybox-sample-statefulset
+patches:
+  - target:
+      kind: Subscription
+      name: busybox-sub
+    patch: |-
+      - op: replace
+        path: /metadata/annotations/apps.open-cluster-management.io~1github-path
+        value: busybox-statefulset