Fix path to answer file

windows_2016_core.json

@@ -124,6 +124,6 @@
     "iso_url": "http://care.dlservice.microsoft.com/dl/download/1/6/F/16FA20E6-4662-482A-920B-1A45CF5AAE3C/14393.0.160715-1616.RS1_RELEASE_SERVER_EVAL_X64FRE_EN-US.ISO",
     "iso_checksum_type": "md5",
     "iso_checksum": "18a4f00a675b0338f3c7c93c4f131beb",
-    "autounattend": "./answer_files/2016/Autounattend.xml"
+    "autounattend": "./answer_files/2016_core/Autounattend.xml"
   }
 }