do not respawn cancelled threads if we are shutting down

src/charon/processing/processor.c

@@ -84,7 +84,9 @@ static void restart(private_processor_t *this)
 {
 	pthread_t thread;
 	
-	if (pthread_create(&thread, NULL, (void*)process_jobs, this) != 0)
+	/* respawn thread if required */
+	if (this->desired_threads == 0 ||
+		pthread_create(&thread, NULL, (void*)process_jobs, this) != 0)
 	{
 		this->mutex->lock(this->mutex);
 		this->total_threads--;