tokenserver: Extract rules check into a separate function.

tokenserver/appengine/impl/services/admin/adminsrv/service.go

 // Copyright 2016 The LUCI Authors.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //      http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 41 matching lines @@
                         Signer: signer,
                 },
                 InspectMachineTokenRPC: machinetoken.InspectMachineTokenRPC{
                         Signer: signer,
                 },
                 ImportServiceAccountsConfigsRPC: serviceaccounts.ImportServiceAccountsConfigsRPC{
                         RulesCache: serviceaccounts.GlobalRulesCache,
                 },
                 InspectOAuthTokenGrantRPC: serviceaccounts.InspectOAuthTokenGrantRPC{
                         Signer: signer,
+                        Rules:  serviceaccounts.GlobalRulesCache.Rules,
                 },
         }
 }