fedora mirroring: use --delete-delay

[Gokdeniz Karadag]

Hi,

The current mirroring instructions at [1] state that mirrors should give
--delete-after parameter to rsync. A debian mailing list post[2], and rsync man
page state that using --delete-delay improves performance. That option sould be
mentioned at [1] along with the notice that it is available for versions of
rsync >= 3.0

 [1]: http://fedoraproject.org/wiki/Infrastructure/Mirroring#Mirroring
 [2]: http://lists.debian.org/debian-mirrors/2009/04/msg00017.html

-- 
Gokdeniz Karadag