Fix memory info on FreeBSD. (#8620)
Fix memory info on FreeBSD. (#8620)

The obtained process_rss was incorrect (the OS reports pages, not
bytes), resulting with many other fields getting corrupted.

This has been tested on FreeBSD but not other platforms.
JackieXie168/redis,JackieXie168/redis,JackieXie168/redis,JackieXie168/redis