Correctly handle secret and configMap envs in kubectl describe

hack/testdata/pod-with-api-env.yaml

@@ -0,0 +1,25 @@
+apiVersion: v1
+kind: Pod
+metadata:
+  name: env-test-pod
+spec:
+  containers:
+    - name: test-container
+      image: gcr.io/google_containers/busybox
+      command: [ "/bin/sh", "-c", "env" ]
+      env:
+        - name: TEST_CMD_1
+          valueFrom:
+            secretKeyRef:
+              name: test-secret
+              key: key-1
+        - name: TEST_CMD_2
+          valueFrom:
+            configMapKeyRef:
+              name: test-configmap
+              key: key-2
+        - name: TEST_CMD_3
+          valueFrom:
+            fieldRef:
+              fieldPath: metadata.name
+  restartPolicy: Never