make git-push a bit more verbose

Currently git-push displays progress status for the local packing of
objects to send, but nothing once it starts to push it over the
connection.  Having progress status in that later case is especially
nice when pushing lots of objects over a slow network link.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>