Add hostname to API Reference

This patch set adds hostname attribute to Audit and
ActionPlan resources in API Reference.

Change-Id: I187d44dc401d3d1770452022b8610570d459cc98

api-ref/source/samples/audit-create-response.json

@@ -47,5 +47,6 @@
     ],
     "strategy_name": "workload_stabilization",
     "next_run_time": null,
-    "updated_at": null
+    "updated_at": null,
+    "hostname": null
 }