Centralized thread cancellation in processor_t

This ensures that no threads are active when plugins and the rest of the
daemon are unloaded.

callback_job_t was simplified a lot in the process as its main
functionality is now contained in processor_t.  The parent-child
relationships were abandoned as these were only needed to simplify job
cancellation.

src/libcharon/plugins/duplicheck/duplicheck_notify.c

@@ -42,11 +42,6 @@ struct private_duplicheck_notify_t {
 	 */
 	duplicheck_notify_t public;
 
-	/**
-	 * Callback job dispatching connections
-	 */
-	callback_job_t *job;
-
 	/**
 	 * Mutex to lock list
 	 */
@@ -167,10 +162,6 @@ METHOD(duplicheck_notify_t, destroy, void,
 	enumerator_t *enumerator;
 	uintptr_t fd;
 
-	if (this->job)
-	{
-		this->job->cancel(this->job);
-	}
 	enumerator = this->connected->create_enumerator(this->connected);
 	while (enumerator->enumerate(enumerator, &fd))
 	{
@@ -203,9 +194,9 @@ duplicheck_notify_t *duplicheck_notify_create()
 		destroy(this);
 		return NULL;
 	}
-	this->job = callback_job_create_with_prio((callback_job_cb_t)receive,
-									this, NULL, NULL, JOB_PRIO_CRITICAL);
-	lib->processor->queue_job(lib->processor, (job_t*)this->job);
+	lib->processor->queue_job(lib->processor,
+		(job_t*)callback_job_create_with_prio((callback_job_cb_t)receive, this,
+				NULL, (callback_job_cancel_t)return_false, JOB_PRIO_CRITICAL));
 
 	return &this->public;
 }