It was accepting 3 arguments where first one was "build_modules".
It wasn't used anywhere in that function so it was removed from
it.
This patch reflects that Devstack change in the Neutron's functional
tests script too.
Closes-Bug: #1957887
Depends-On: https://review.opendev.org/c/openstack/devstack/+/822717
Change-Id: Id8302bf23f48b227d05f1ec2a7136935b7b1c2fb