Fix client not exiting via signals (INT/TERM)

Fixed by removing extraneous call to System.exit() in Controller.stopAll()

Most callers of Controller.stopAll(), i.e. other classes, also call
System.exit() themselves afterwards.

Controller class also sets up a shutdown hook which calls stopAll()
but the [now removed] extra call to System.exit() inside stopAll()
was blocking and stopping proper shutdown, requiring SIGKILL.

Qora/src/controller/Controller.java

@@ -634,8 +634,6 @@ public void stopAll() {
 			createDataCheckpoint();
 
 			LOGGER.info(Lang.getInstance().translate("Closed."));
-			// FORCE CLOSE
-			System.exit(0);
 		}
 	}