Replace ETA with used time when finished

[lightonflux]

When a download finished you see something like:

[download] 100.0% of 16.35MiB at  7.50KiB/s ETA 00:00

Which is logical, but no really helpful to the end user.

It would be great if yt-dl could display the used time instead if an useless ETA.

Like this:

[download] 100.0% of 612.35MiB at  7.50MiB/s in 01:36

[jaimeMF]

A similar solution was posted in #1181

[jaimeMF]

Fixed by @h3xx.