Add a minimum delay before block finalization
Summary:
This prevents a recently received block to get finalized.
Test Plan:
./test/functional/abc-finalize-block.py
Reviewers: #bitcoin_abc, schancel, deadalnix, jasonbcox
Reviewed By: #bitcoin_abc, schancel, deadalnix, jasonbcox
Subscribers: jasonbcox, schancel
Differential Revision: https://reviews.bitcoinabc.org/D2132