fix regressions around output vars (#845)

Author: anhowe

parts/dcosmastervars.t

@@ -45,6 +45,8 @@
     "storageAccountPrefixes": [ "0", "6", "c", "i", "o", "u", "1", "7", "d", "j", "p", "v", "2", "8", "e", "k", "q", "w", "3", "9", "f", "l", "r", "x", "4", "a", "g", "m", "s", "y", "5", "b", "h", "n", "t", "z" ], 
     "storageAccountPrefixesCount": "[length(variables('storageAccountPrefixes'))]", 
     {{GetSizeMap}},
+{{else}}
+    "storageAccountPrefixes": [],
 {{end}}
 {{if .HasManagedDisks}}
     "apiVersionStorageManagedDisks": "2016-04-30-preview",

parts/swarmmastervars.t

@@ -122,6 +122,9 @@
     "vmsPerStorageAccount": 20,
     "storageAccountBaseName": "[uniqueString(concat(variables('masterEndpointDNSNamePrefix'),variables('location')))]",
     {{GetSizeMap}},
+{{else}}
+    "storageAccountPrefixes": [],
+    "storageAccountBaseName": "",
 {{end}}
 {{if .HasManagedDisks}}
     "apiVersionStorageManagedDisks": "2016-04-30-preview",