NIFI-7079 Changed flow fingerprinting implementation

[alopresto]

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Changes the flow fingerprinting implementation.

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[markap14]

Thanks @alopresto! Code looks good. Did some testing with a 3-node cluster. Started up, then restarted cluster. Restarted one of the nodes individually. All worked. Then shutdown one node, removed it from cluster so that I could modify the dataflow. Changed a relevant field on a processor. Then restarted the node. It successfully downloaded the flow, detected that the flow was different, and failed to startup. The explanation provided in the log was as expected. +1