This entry point is called when the this instance of the plugin is no
longer needed (the Job is ending), and the plugin should release all
memory it may have allocated for this particular instance (Job) i.e. the
pContext. This is not the final termination of the plugin signaled by a
call to unloadPlugin. Any other instances (Job) will continue to
run, and the entry point newPlugin may be called again if other jobs
start.