kern/54370: lib/libc/sys/t_getitimer/setitimer_old test case fails randomly

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         54370
>Category:       kern
>Synopsis:       lib/libc/sys/t_getitimer/setitimer_old test case fails randomly
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Jul 11 19:45:00 +0000 2019
>Originator:     Andreas Gustafsson
>Release:        NetBSD 8.1, -current
>Organization:

>Environment:
System: NetBSD
Architecture: x86_64
Machine: amd64
>Description:

The setitimer_old test case of the lib/libc/sys/t_getitimer test randomly
fails with the message "FAILED: setitimer(2) did not store old values".

I have reproduced this in -current/i386 under qemu and 8.1/amd64 on
real hardware.

>How-To-Repeat:

This usually triggers a failure in less than a minute for me:

 cd /usr/tests/lib/libc/sys
 while ./t_getitimer setitimer_old; do true; done

>Fix: