token-server: Fix panic when generating machine token for unrecognized machine.

tokenserver/appengine/impl/machinetoken/rpc_inspect_machine_token_test.go

 // Copyright 2016 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package machinetoken
 
 import (
         "crypto/x509/pkix"
         "math/big"
         "testing"
         "time"
 
         "github.com/luci/luci-go/common/clock"
         "github.com/luci/luci-go/common/clock/testclock"
 
         tokenserver "github.com/luci/luci-go/tokenserver/api"
         admin "github.com/luci/luci-go/tokenserver/api/admin/v1"
         "github.com/luci/luci-go/tokenserver/appengine/impl/certconfig"
 
         . "github.com/smartystreets/goconvey/convey"
 )
 
 func TestInspectMachineTokenRPC(t *testing.T) {
         Convey("with mocked context", t, func() {
-                ctx := testingContext()
+                ctx := testingContext(testingCA)
                 impl := InspectMachineTokenRPC{
                         Signer: testingSigner(),
                 }
                 tok := expectedLuciMachineToken
 
                 Convey("Good token", func() {
                         reply, err := impl.InspectMachineToken(ctx, &admin.InspectMachineTokenRequest{
                                 TokenType: tokenserver.MachineTokenType_LUCI_MACHINE_TOKEN,
                                 Token:     tok,
                         })
@@ skipping 105 matching lines @@
                                                 IssuedAt:    1422936306,
                                                 Lifetime:    3600,
                                                 CaId:        123,
                                                 CertSn:      4096,
                                         },
                                 },
                         })
                 })
         })
 }