Make sure wallet.py works with the fork enabled

Summary:
This ensure it uses replay protected transactions and do not check for big blocks rejection.

Depends on D432

Test Plan: Run the test.

Reviewers: freetrader, CCulianu, hanchon, #bitcoin_abc

Reviewed By: CCulianu, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D435