MFC 326953:

MFC 326953:
Catch up to r325719 which makes the kern.proc.pid sysctl "work" for zombies.

Some of the ptrace tests need to wait for a child process to become a
zombie before preceding.  The parent process polls the child process
via the kern.proc.pid sysctl to wait for it to become a zombie.
Previously the code polled until the sysctl failed with ESRCH.  Now it
will poll until either the sysctl fails with ESRCH (for compatiblity
with older kernels) or returns a kinfo_proc structure with the ki_stat
field set to SZOMB.

git-svn-id: svn://svn.freebsd.org/base/stable/10@328309 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f