t5541: run "used receive-pack service" test earlier

t5541: run "used receive-pack service" test earlier

There's a test in t5541 that confirms that "git push" makes two requests
(a GET to /info/refs, and a POST to /git-receive-pack). However, it's a
noop unless GIT_TEST_PROTOCOL_VERSION is set to "0", due to 8a1b0978ab
(test: request GIT_TEST_PROTOCOL_VERSION=0 when appropriate,
2019-12-23).

This means that almost nobody runs it. And indeed, it has been broken
since b0c4adcdd7 (remote-curl: send Accept-Language header to server,
2022-07-11). But the fault is not in that commit, but in how brittle the
test is. It runs after several operations have been performed, which
means that it expects to see the complete set of requests made so far in
the script. Commit b0c4adcdd7 added a new test, which means that the
"used receive-pack service" test must be updated, too.

Let's fix this by making the test less brittle. We'll move it higher in
the script, right after the first push has completed. And we'll clear
the access log right before doing the push, so we'll see only the
requests from that command.

This is technically testing less, in that we won't check that all of
those other requests also correctly used smart http. But there's no
particular reason think that if the first one did, the others wouldn't.

After this patch, running:

  GIT_TEST_PROTOCOL_VERSION=0 ./t5541-http-push-smart.sh

passes, whereas it did not before.

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