Fix missing comma for empty arrays/sets

When an array or a set is empty, and if it's not the last property
within an object, we need to add a comma after empty brackets/braces.

This change fix this issue. Also updated a test case to capture this.

Signed-off-by: Kasun Athukorala <kasunath@google.com>
Change-Id: Ia087f341d052660191f2614add2060c81be67f61
diff --git a/test/json/storage.json b/test/json/storage.json
index 007c4ff..df43ead 100644
--- a/test/json/storage.json
+++ b/test/json/storage.json
@@ -10,6 +10,7 @@
       "Health": "OK",
       "HealthRollup": "OK"
    },
+   "@Message.ExtendedInfo": [],
    "StorageControllers": [
       {
          "@odata.id": "/redfish/v1/Systems/1/Storage/1#/StorageControllers/0",
@@ -75,5 +76,5 @@
    "@Redfish.CollectionCapabilities": {
       "MaxMembers": 0
    },
-   "@Message.ExtendedInfo": []
+   "Redundancy" : []
 }