Imagine following situation:
- Long time ago a_service was started through rc.d
- We want to restart a_service and issue
service a_service restart
- rc.subr reads current process PID (via file or process), sends TERM signal and runs pwait with PID harvested
- a_service process dies very quickly so it's PID becomes available. It is possible that while original process was running PID counter overflowed and pwait can get a_service's PID as it's own PID trapping itself in a dealock.
This patch ignores pid(s) to wait that are equal to pwait PID.