Simplify progress reprort for the UTXO DB upgrade

Summary: Remove code duplication.

Test Plan:

ninja all check

Force run the UTXO upgrade by removing the guard line 380, loading the new UTXOs but not do anything with them.

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D8315