Rename function in bip65 integration test so it does not collide with create_transaction

Summary: Eliminate confusion while testing

Test Plan: Read it. This test is not passing at this time.

Reviewers: deadalnix, schancel, #bitcoin_abc, Fabien

Reviewed By: schancel, #bitcoin_abc, Fabien

Subscribers: teamcity, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D2069