make sure throughput display gets updated even if progress doesn't move

make sure throughput display gets updated even if progress doesn't move

Currently the progress/throughput display update happens only through
display_progress().  If the progress based on object count remains
unchanged because a large object is being received, the latest throughput
won't be displayed.  The display update should occur through
display_throughput() as well.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>