add v1 tests to hack/test-go; let default value of Container.SecurityContext to be nil

pkg/api/validation/testdata/v1/invalidPod.yaml

@@ -0,0 +1,11 @@
+apiVersion: v1
+kind: Pod
+metadata:
+  labels:
+    name: redis-master
+  name: name
+spec:
+  containers:
+  - args: "this is a bad command"
+    image: redis
+    name: master