progress bar: always update when at 100%

Currently, the progress bar is updated at 5Hz. Because it is often not
updated to 100% when the download is finished and curl exits, the bar
is often "stuck" at 90-something, thus irritating the user.

This patch fixes this by always updating the progress bar (instead of
waiting for 200ms to have elapsed) while the download is finished but
curl has not yet exited. This should not greatly affect performance
because that moment is rather short.

Signed-off-by: Tobias Markus <tobias@markus-regensburg.de>