trivial: Suggested cleanups to surrounding code

Summary:
https://github.com/bitcoin/bitcoin/pull/18982#pullrequestreview-416974841

This is a backport of core#18982 [2/2]
https://github.com/bitcoin/bitcoin/pull/18982/commits/7eaf86d3bfc83f2beb3ef449707d5156853126fb

Depends on D9962

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Subscribers: majcosta

Differential Revision: https://reviews.bitcoinabc.org/D9963