Only parse complex types if there is a value

This tries to bring it inline with the other value() methods.

Change-Id: Ib749c44127862b054a01ee74b3e1a716f7b637e8
Closes-bug: 1424600
diff --git a/functional/test_autoscaling.py b/functional/test_autoscaling.py
index 15b318b..60fa66f 100644
--- a/functional/test_autoscaling.py
+++ b/functional/test_autoscaling.py
@@ -70,7 +70,7 @@
   InstanceType: {type: string}
   SecurityGroups: {type: comma_delimited_list}
   UserData: {type: string}
-  Tags: {type: comma_delimited_list}
+  Tags: {type: comma_delimited_list, default: "x,y"}
 
 resources:
   random1:
@@ -93,7 +93,7 @@
   InstanceType: {type: string}
   SecurityGroups: {type: comma_delimited_list}
   UserData: {type: string}
-  Tags: {type: comma_delimited_list}
+  Tags: {type: comma_delimited_list, default: "x,y"}
 
 resources:
   random1:
@@ -612,7 +612,7 @@
   InstanceType: {type: string}
   SecurityGroups: {type: comma_delimited_list}
   UserData: {type: string}
-  Tags: {type: comma_delimited_list}
+  Tags: {type: comma_delimited_list, default: "x,y"}
 
 resources:
 outputs: