"remote update": print remote name being fetched from

When the other end has dangling symref, "git fetch" issues an error
message but that is not grave enough to cause the fetch process to fail.
As the result, the user will see something like this:

$ git remote update
error: refs/heads/2.0-uobjects points nowhere!

"remote update" used to report which remote it is fetching from, like
this:

$ git remote update
Updating core
Updating matthieu
error: refs/heads/2.0-uobjects points nowhere!
Updating origin

This reinstates the message "Updating <name>" in "git remote update".

Signed-off-by: Samuel Tardieu <sam@rfc1149.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>