qa: Add multiwallet prefix test

Summary:
Merge #11743: qa: Add multiwallet prefix test

fa61c6f6a qa: Add multiwallet prefix test (MarcoFalke)

Pull request description:

Fixes https://github.com/bitcoin/bitcoin/pull/10849#discussion_r127847938

Tree-SHA512: 7967be04e76d935398b3bea60c864ffc9e38dbb4cfb55890bb146a6f16c28d81ca5d89736275e2d0b03642806f6f7093beeea979f5257c464f437c4e5a9684f1

Core PR11743

Fixes T177

Test Plan: ./test/functional/test_runner.py multiwallet

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: teamcity

Maniphest Tasks: T177

Differential Revision: https://reviews.bitcoinabc.org/D1055