load incorrect memory size, should use cgroupfs instead of procfs

[STRRL]

I just noticed that we're using this library for fetching max available mem:

memStress/main.go

Line 117 in 6583ea9

memInfo, _ := psutil.VirtualMemory()

in the source code, it use procfs to get meminfo:

https://github.com/shirou/gopsutil/blob/c95f835cd977d7aa68f61d7ea06e452cac789927/mem/mem_linux.go#L34

in a container, the procfs does NOT represent the resources in cgroupfs.

[STRRL]

related issue: chaos-mesh/chaos-mesh#4547