nits in abc-replay-protection
nits in abc-replay-protection

Summary: Fixes a couple of nits pointed out by Fabien in D2527 and D2483.

Test Plan: run the functional test

Reviewers: #bitcoin_abc, deadalnix, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: teamcity, Fabien, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2539

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