Replace spammy log message in dscache with comment.

filter/dscache/ds.go

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package dscache
 
 import (
         "time"
 
         ds "github.com/luci/gae/service/datastore"
@@ skipping 22 matching lines @@
         })
 }
 
 func (d *dsCache) GetMulti(keys []*ds.Key, metas ds.MultiMetaGetter, cb ds.GetMultiCB) error {
         lockItems, nonce := d.mkRandLockItems(keys, metas)
         if len(lockItems) == 0 {
                 return d.RawInterface.GetMulti(keys, metas, cb)
         }
 
         if err := d.mc.AddMulti(lockItems); err != nil {
-                (log.Fields{log.ErrorKey: err}).Warningf(
-                        d.c, "dscache: GetMulti: memcache.AddMulti")
-
+                // Ignore this error. Either we couldn't add them because they exist
+                // (so, not an issue), or because memcache is having sad times (in which
+                // case we'll see so in the GetMulti which immediately follows this).
         }
         if err := d.mc.GetMulti(lockItems); err != nil {
                 (log.Fields{log.ErrorKey: err}).Warningf(
                         d.c, "dscache: GetMulti: memcache.GetMulti")
         }
 
         p := makeFetchPlan(d.c, d.aid, d.ns, &facts{keys, metas, lockItems, nonce})
 
         if !p.empty() {
                 // looks like we have something to pull from datastore, and maybe some work
@@ skipping 76 matching lines @@
                 if err == nil {
                         err = txnState.apply(d.supportContext)
                 }
                 return err
         }, opts)
         if err == nil {
                 txnState.release(d.supportContext)
         }
         return err
 }