Fix bip65-cltv-p2p test for pre-fork conditions

Summary: Fixes this test to pass as it did pre-fork. This does *not* fix the test for post-fork testing, but gives us a passing test to build forward on.

Test Plan: test_runner.py bip65-cltv-p2p

Reviewers: deadalnix, schancel, #bitcoin_abc

Reviewed By: deadalnix, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D2070