remote-curl: don't retry auth failures with dumb protocol

remote-curl: don't retry auth failures with dumb protocol

When fetching an http URL, we first try fetching info/refs
with an extra "service" parameter. This will work for a
smart-http server, or a dumb server which ignores extra
parameters when fetching files. If that fails, we retry
without the extra parameter to remain compatible with dumb
servers which didn't like our first request.

If the server returned a "401 Unauthorized", indicating that
the credentials we provided were not good, there is not much
point in retrying. With the current code, we just waste an
extra round trip to the HTTP server before failing.

But as the http code becomes smarter about throwing away
rejected credentials and re-prompting the user for new ones
(which it will later in this series), this will become more
confusing. At some point we will stop asking for credentials
to retry smart http, and will be asking for credentials to
retry dumb http. So now we're not only wasting an extra HTTP
round trip for something that is unlikely to work, but we're
making the user re-type their password for it.

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