We discovered this in Hudson v1.309. When a slave is configured with an idle
delay, it eventually shuts down due to inactivity. When this happens, the
Hudson master seems to be unable to distinguish this condition from a genuine
failure, and marks the slave as offline. If the slave is also configured with
an on-demand delay, then Hudson will attempt to start the slave if its job queue
is non-empty for the specified time, but will fail because it thinks the slave
has failed.