Improve command package isolation.

pkg/commands/build/testdata/testcase-single-overlay/in/package/deployment.yaml

@@ -0,0 +1,24 @@
+apiVersion: apps/v1beta2
+kind: Deployment
+metadata:
+  name: nginx
+  labels:
+    app: nginx
+spec:
+  template:
+    metadata:
+      labels:
+        app: nginx
+    spec:
+      containers:
+      - name: nginx
+        image: nginx
+        volumeMounts:
+        - name: nginx-persistent-storage
+          mountPath: /tmp/ps
+      volumes:
+      - name: nginx-persistent-storage
+        emptyDir: {}
+      - configMap:
+          name: configmap-in-base
+        name: configmap-in-base