avoid bogus log messages in worker

From http://tracker.nagios.org/view.php?id=534

When using service_perfdata_command or host_perfdata_command configuration
Nagios logs a warning message for each service/host check. These warning
messages look like:

[1383116400] Worker 1277: Unknown jobtype: 10
[1383116400] wproc: Unknown job type: 10
[1383116400] Worker 1279: Unknown jobtype: 10
[1383116400] wproc: Unknown job type: 10
[1383116400] Worker 1278: Unknown jobtype: 10
[1383116400] wproc: Unknown job type: 10

Reported-by: ovidiu_stanila
Original-patch-by: ovidiu_stanila
Signed-off-by: Sven Nierlein <Sven.Nierlein@consol.de>