Refine checkpoint handling in Subserver and remove unnecessary debug logs in CheckpointUtilsJ9

SpigotCore/SpigotCore_Main/src/de/steamwar/core/CheckpointUtilsJ9.java

@@ -121,7 +121,6 @@ class CheckpointUtilsJ9 {
         } catch (JVMCRIUException e) {
             Path logfile = path.resolve("criu.log");
             if(logfile.toFile().exists()) {
-                System.out.println("Reading criu log");
                 throw new IllegalStateException("Could not create checkpoint, criu log:\n" + new String(Files.readAllBytes(logfile)), e);
             }
 
@@ -134,8 +133,6 @@ class CheckpointUtilsJ9 {
             port = stream.readInt();
         }
 
-        System.out.println(port);
-
         // Reopen socket
         bind.invoke(serverConnection, InetAddress.getLoopbackAddress(), port);
         if(Core.getVersion() > 12) {

VelocityCore/Persistent/src/de/steamwar/persistent/Subserver.java

@@ -220,6 +220,7 @@ public class Subserver {
         try {
             if (checkpoint) {
                 start(process.getErrorStream(), line -> line.contains("Restore finished successfully."));
+                Thread.sleep(300);
             } else {
                 start(process.getInputStream(), line -> {
                     if (line.contains("Loading libraries, please wait"))