Fix bunch of fd leaks in http-fetch

Fix bunch of fd leaks in http-fetch

The current http-fetch is rather careless about fd leakage, causing
problems while fetching large repositories. This patch does not reserve
exhaustiveness, but I covered everything I spotted. I also left some
safeguards in place in case I missed something, so that we get to know,
sooner or later.

Reported by Becky Bruce <becky.bruce@freescale.com>.

Signed-off-by: Petr Baudis <pasky@suse.cz>
Signed-off-by: Junio C Hamano <junkio@cox.net>