Do not give alarming error message from rsync in fetch and clone.

When we check the optional objects/info/alternates file at the remote
repository, we forgot to really squelch error message from rsync.

Not having that file is not a crime.

Signed-off-by: Junio C Hamano <junkio@cox.net>
(cherry picked from 89d844d084f14bc9506f63cd3c9aa44b21b49067 commit)