t5541: mark passing c-a-s test as success

Commit 05c1eb1 (push: teach --force-with-lease to smart-http
transport) fixed the compare-and-swap test in t5541. It
tried to mark the test as passing by teaching the test
helper function to expect an extra "success or failure"
parameter, but forgot to actually use the parameter in the
helper.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>