DO NOT MERGE ANYWHERE: [AsyncChannel] Fix race in handling of sync result am: 02d802e71e  -s ours am: b5ee561702  -s ours am: 7391bedf87  -s ours
am: 8597268bc2  -s ours

Change-Id: I57d0fa2972f5f93ca0c12455873ce05356d6ebf4