Incorrect I/O in process bar

[ClementTsang]

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Note that this is already fixed in this commit; I'm filing this for documentation purposes.

The problem was that the R/s, W/S, total read, and total write columns were pulling the wrong data from /proc/<PID>/io in Linux systems.

This did not affect macOS or Windows since I use a library for that, but I write my own harvesters for Linux.