PR9739 backport. Seems we missed it. I noticed the same logic bug
(the `assert not before_activation` is useless because it just gets
covered up by the `except:` suppression!).
f5aba8a Move tx version 2 standardness check to after bip68 activation (John Newbery)
99c0e81 Fix BIP68 activation test (John Newbery)