Add service update changelog

Author: dagnir

.changes/next-release/feature-AWSSDKforJavav2-8138f04.json

@@ -0,0 +1,5 @@
+{
+    "category": "AWS SDK for Java v2", 
+    "type": "feature", 
+    "description": "Update service models to be current as of 2018-09-07."
+}