[BUG] Race condition in DataPrepper sources using e2e acknowledgements

[kkondaka]

Describe the bug
Race condition in DataPrepper sources using e2e acknowledgements.
DataPrepper sources using e2e acknowledgements are doing something like this

bufferAccumulator.add(eventRecord); 
if(Objects.nonNull(acknowledgementSet)){                                                                                                 
      acknowledgementSet.add(eventRecord.getData());                                                                                       
}                                                                                                                                        

This may result in eventRecord getting processed (and may even be dropped, if drop processor is used) even before the event Record is added tot he acknowledgement set.

To Reproduce
Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior
Expected behavior is that the event record is added to the acknowledgement set before it is processed further by the pipeline.
Fix is to swap the lines as shown below

if(Objects.nonNull(acknowledgementSet)){                                                                                                 
      acknowledgementSet.add(eventRecord.getData());                                                                                       
}      
bufferAccumulator.add(eventRecord); 

Screenshots
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Environment (please complete the following information):

• OS: [e.g. Ubuntu 20.04 LTS]
• Version [e.g. 22]

Additional context
Add any other context about the problem here.