Api method GetById can return NotFound for started batch

[DnikitaA]

if you run multiple SampleBatch.Service instances, you can get a race condition. A situation may arise when different instances of SampleBatch.Service capture messages BatchReceived and StateRequested at the same time with the same BatchId. And then BatchStateMachine will return BatchNotFound, since BatchState at this moment has not yet been saved to the database.