Fix 'impl/memory' context key.

impl/memory/datastore.go

 // Copyright 2015 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 memory
 
 import (
         "errors"
         "fmt"
 
@@ skipping 201 matching lines @@
 
 func (d *txnDsImpl) Count(fq *ds.FinalizedQuery) (ret int64, err error) {
         return countQuery(fq, d.kc, true, d.data.snap, d.data.snap)
 }
 
 func (*txnDsImpl) RunInTransaction(func(c context.Context) error, *ds.TransactionOptions) error {
         return errors.New("datastore: nested transactions are not supported")
 }
 
 func (d *txnDsImpl) WithoutTransaction() context.Context {
-        return context.WithValue(d, currentTxnKey, nil)
+        return context.WithValue(d, &currentTxnKey, nil)
 }
 
 func (d *txnDsImpl) CurrentTransaction() ds.Transaction {
         return d.data.txn
 }
 
 func (d *txnDsImpl) GetTestable() ds.Testable { return nil }