Fix information leak. We can find PIDs of running processes from within a jail, etc. by simply calling setpriority(PRIO_PROCESS, <PID>, 0) and checking the return value: 0 means that the process exists and -1 that it doesn't exist.
Fix information leak. We can find PIDs of running processes from within
a jail, etc. by simply calling setpriority(PRIO_PROCESS, <PID>, 0) and
checking the return value: 0 means that the process exists and -1 that
it doesn't exist.

Reviewed by:	rwatson
MFC after:	1 week

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