test: Fix test failures

Summary:
From Core's conversation:

in feature_dbcrash:

    Fixes #16488
    Fixes #16498

Backport of core PR16493:
https://github.com/bitcoin/bitcoin/pull/16493/files

Depends on D4560.

Test Plan:

./test/functional/test_runner.py feature_dbcrash

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D4565