Controls when Jenkins starts and stops the slave.

Keep this slave on-line as much as possible
  This is the default and normal setting. In this mode, Jenkins uses tries to keep the slave on-line. If Jenkins can start the slave without user assistance, it will periodically attempt to restart the slave if it is unavailable. Jenkins will not take the slave off-line.
Take this slave on-line when in demand and off-line when idle
  In this mode, if Jenkins can launch the slave without user assistance, it will periodically attempt to launch the slave while there are unexecuted jobs which meet the following criteria:
  - They have been in the queue for at least the specified startup demand period
  - They can execute on this slave
  The slave will be taken off-line if:
  - There are no active jobs running on the slave
  - The slave has been idle for at least the specified idle period