Fix Secret check_mode (#343)

When adding a Secret and using stringData, check_mode will always show
changes. An existing resource fetched from Kubernetes will have the
stringData already base64 encoded and merged into the data attribute.
This change performs the base64 encoding and merging with the provided
definition to more accurately represent the current state of the
cluster.

This change only affects check_mode. When making any changes to the
cluster the stringData is passed along as provided in the definition.

Closes #282.

molecule/default/tasks/apply.yml

@@ -761,6 +761,81 @@
         that:
           - deploy_after_serviceaccount_removal is failed
 
+    - name: Add a secret
+      k8s:
+        definition:
+          apiVersion: v1
+          kind: Secret
+          metadata:
+            name: apply-secret
+            namespace: "{{ apply_namespace }}"
+          type: Opaque
+          stringData:
+            foo: bar
+      register: k8s_secret
+
+    - name: Check secret was created
+      assert:
+        that:
+          - k8s_secret is changed
+          - k8s_secret.result.data.foo
+
+    - name: Add same secret
+      k8s:
+        definition:
+          apiVersion: v1
+          kind: Secret
+          metadata:
+            name: apply-secret
+            namespace: "{{ apply_namespace }}"
+          type: Opaque
+          stringData:
+            foo: bar
+      register: k8s_secret
+
+    - name: Check nothing changed
+      assert:
+        that:
+          - k8s_secret is not changed
+
+    - name: Add same secret with check mode on
+      k8s:
+        definition:
+          apiVersion: v1
+          kind: Secret
+          metadata:
+            name: apply-secret
+            namespace: "{{ apply_namespace }}"
+          type: Opaque
+          stringData:
+            foo: bar
+      check_mode: yes
+      register: k8s_secret
+
+    - name: Check nothing changed
+      assert:
+        that:
+          - k8s_secret is not changed
+
+    - name: Add same secret with check mode on using data
+      k8s:
+        definition:
+          apiVersion: v1
+          kind: Secret
+          metadata:
+            name: apply-secret
+            namespace: "{{ apply_namespace }}"
+          type: Opaque
+          data:
+            foo: YmFy
+      check_mode: yes
+      register: k8s_secret
+
+    - name: Check nothing changed
+      assert:
+        that:
+          - k8s_secret is not changed
+
   always:
     - name: Remove namespace
       k8s: