Fix possible data race in manager/state/store/memory_test.go
Fix possible data race in manager/state/store/memory_test.go

Signed-off-by: Vincent Robbemond <92c4fe75cfcda6bf658e5838b4ba699c50f043d3@gmail.com>

dperny/swarmkit-1,dperny/swarmkit-1,docker/swarmkit,docker/swarmkit