Use correct unit when parsing memory and swap from Linux

[ClementTsang]

Switch to treating parsed values from /proc/meminfo as kibibytes. Previously, it was treated as kilobytes, but apparently that's not correct, as per this Red Hat doc:

While the file shows kilobytes (kB; 1 kB equals 1000 B), it is actually kibibytes (KiB; 1 KiB equals 1024 B). This imprecision in /proc/meminfo is known, but is not corrected due to legacy concerns - programs rely on /proc/meminfo to specify size with the "kB" string.

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Fixes: #341