Fix pkill unit tests.

- use daemon(8) to write out a pid file for processes,
  and check for for the existence of that file after
  killing processes
- use explict named parameters to jail(8)
Merge remote-tracking branch 'freebsd/master' into hardened/current/master
Merge remote-tracking branch 'origin/hardened/current/master' into hardened/current/aslr