update CloudFormation/Memcached.yaml.

CloudFormation/Memcached.yaml

@@ -14,6 +14,7 @@ Resources:
   cachecluster:
     Type: 'AWS::ElastiCache::CacheCluster'
     Properties:
+      AZMode: cross-az
       Engine: memcached
       ClusterName: cachecluster
       NumCacheNodes: '2'