Adjust vm.max_wired in order to avoid hitting EAGAIN artificially

[ngie]

Summary

Adjust vm.max_wired in order to avoid hitting EAGAIN artificially

Set vm.max_wired to INT_MAX in :mlock_err, :mlock_mmap, and :mlock_nested to
avoid hitting EAGAIN artificially on the system when running the tests

Require root privileges in order to set the sysctl

Add allow_sysctl_side_effects to require.config as this test is now adjusting
sysctls that can affect the global system state

MFC after: 1 week
Obtained from: Isilon OneFS (^/onefs/head@r511419)
Sponsored by: EMC / Isilon Storage Division

[cem]

Please take me off "submitted by" — I didn't write this patch. I suggested the use of vm.max_wired as a workaround but my patch looked a lot different.

contrib/netbsd-tests/lib/libc/sys/t_mlock.c

97–98

I'm not sure what purpose writing out a "vm.max_wired" file serves.

[ngie]

contrib/netbsd-tests/lib/libc/sys/t_mlock.c

97–98

I'm using a file as scratch to save/restore the previous state of the sysctl. Code that "does things" (runs a sysctl, creates a file, etc) shouldn't be done in ATF_TP_ADD_TCS (that's what the code we have in OneFS does today in Riptide).

This code is always executed, but only once (the old code did it more than once in the successful case, IIRC..).