NIFI-4028 - fix cache update when Wait releases flow files

[pvillard31]

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[ijokarumawak]

Hi @pvillard31 , thanks for tackling this! Although the proposed change can keep a signal when there are counts remaining, I found that:

• Current implementation of Wait and WaitNotifyProtocal are already complex, and adding another execution branch would make it more complex, and hard to maintain
• Calling WaitNotifyProtocol.notify method from Wait is not expected by design.

So, I'd like to propose different approach, that refactors and consolidates current implementation so that Wait processor has less different execution paths in its code. That would be more understandable for developers and users. Would you take a look at this commit? This branch has 1 more commit based on this PR:
ijokarumawak@9bc38bb
If it looks reasonable, please add it to your PR.

[pvillard31]

Thanks @ijokarumawak for your review and work, that's much cleaner with your commit. I just added it to this PR.

[ijokarumawak]

@pvillard31 Local contrib check passed without issue, and tested with different flows. LGTM +1, merging to master. Thanks!