Replace GeneratedFullDataFileHandler wait threads with a timer

It's still a bad solution, but now it won't create several hundred threads, so that's nice

core/src/main/java/com/seibel/distanthorizons/core/file/fullDatafile/GeneratedFullDataFileHandler.java

@@ -46,6 +46,7 @@ import java.util.function.Function;
 public class GeneratedFullDataFileHandler extends FullDataFileHandler
 {
 	private static final Logger LOGGER = DhLoggerBuilder.getLogger();
+	private static final Timer CHUNK_GEN_FINISHED_TIMER = new Timer();
 	
 	private final AtomicReference<IWorldGenerationQueue> worldGenQueueRef = new AtomicReference<>(null);
 	
@@ -275,12 +276,11 @@ public class GeneratedFullDataFileHandler extends FullDataFileHandler
 			// FIXME this is a bad fix to prevent full data sources saving incomplete, causing holes in the world after generation.
 			//  The problem appears to be that the save may be happening too quickly,
 			//  potentially happening before the meta file has the newly generated data added to it.
-			new Thread(() -> 
+			CHUNK_GEN_FINISHED_TIMER.schedule(new TimerTask()
 			{
-				try{ Thread.sleep(4000); }catch (InterruptedException e){}
-				
-				this.flushAndSaveAsync(pos).join();
-			}).start();
+				@Override
+				public void run() { GeneratedFullDataFileHandler.this.flushAndSaveAsync(pos).join(); }
+			}, 4000L);
 			
 			this.fireOnGenPosSuccessListeners(pos);
 			return;