SVN r340744 erroneously changed pfind() to return any process including
zombies and pfind_any() to return only non-zombie processes.
In particular, this caused kill() on a zombie process to fail with [ESRCH].
There is no direct test case for this but
/usr/tests/bin/sh/builtins/kill1.0 occasionally triggers it.
Conversely, returning zombies from pfind() seems likely to violate
invariants and cause panics, but I have not looked at this.