Fix MDBX_EKEYMISMATCH in mining

Set sync stage to FINISH rather than ACCOUNT_HISTORY as they run at the end of mine_block()

Closes #103

changed milestone to %v1: network (submission)

added bug label

requested review from @jerdesch

assigned to @angraign

enabled an automatic merge when the pipeline for cb061735 succeeds

merged

mentioned in commit c84e86d1