[qa] Fix invalidblockrequest to work with magnetic anomaly upgrade

Summary: This update fixes issues with CTOR and CLEANSTACK enforcement after the 15th of November 2018.

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

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Subscribers: teamcity

Differential Revision: https://reviews.bitcoinabc.org/D2082