Fix undefined reseller_prefix_upcase

... because that is now causing an error in testing with Puppet 8.

Change-Id: Id2694286c08e40d2bb6e8e07cf5c47b01712a84b

manifests/proxy/tempauth.pp

@@ -88,6 +88,8 @@ class swift::proxy::tempauth (
   if ($reseller_prefix) {
     validate_legacy(String, 'validate_string', $reseller_prefix)
     $reseller_prefix_upcase = upcase($reseller_prefix)
+  } else {
+    $reseller_prefix_upcase = $reseller_prefix
   }
 
   if ($token_life) {