TestGetProcInodesAll: create a server so there are some opened inodes
TestUsers: skip if Users is empty, because of an empty /var/run/utmp
Test_Process_Groups: skip if Groups is empty
TestConnectionsMax: skip on CI, not only CircleCI
TestHostInfoStat_String has been broken since kernelArch has been
introduced. Fix it.
Also adjust the error message to show the wanted string, aligned with
the gotten string so it's easier to spot differences.
Improve performance by eliminating the fork out to uname on FreeBSD which also helps prevent crashes / hangs due to the outstanding fork crash bug:
golang/go#15658
Also added a test for PlatformInformation.
When fetching stats on all processes at once there's a non-trivial amount of
time spent in the `BootTime` call. But since this value should never change
during a live process, we can use a cached version for all subsequent calls.
This is mostly intended for Linux, where we are returning the OS version
in the PlatformVersion field, which seems reasonable. Often it is still
useful to know which Linux kernel is running.
For FreeBSD and Darwin the kernel version matches the platform version,
since they previously used the kernel version for the platform version.
For Windows the kernel version is empty, since there is no clear way
to determine it.
On supported hosts the value returned is a UUID (case preserving
from the value of the underlying OS).
For Linux this is generated once, randomly per boot. For FreeBSD and
Darwin this is a more durable value that should persist across reboots.
