Do not name "repo" struct "remote" in push_http.c

This patch is a first step in getting http-push to use http authentication
via prompts.  The patch renames remote to repo so that it doesn't get
confusing with the same remote that is passed around when using http.

Signed-off-by: Amos King <amos.l.king@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>