Revert "Use custom async thread execution pool"

This reverts commit a574245bb9.

src/main/java/fr/xephi/authme/service/BukkitService.java

@@ -5,7 +5,6 @@ import fr.xephi.authme.ConsoleLogger;
 import fr.xephi.authme.initialization.SettingsDependent;
 import fr.xephi.authme.settings.Settings;
 import fr.xephi.authme.settings.properties.PluginSettings;
-import fr.xephi.authme.util.Utils;
 import org.bukkit.BanEntry;
 import org.bukkit.BanList;
 import org.bukkit.Bukkit;
@@ -26,10 +25,6 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.Date;
 import java.util.Set;
-import java.util.concurrent.Executor;
-import java.util.concurrent.SynchronousQueue;
-import java.util.concurrent.ThreadPoolExecutor;
-import java.util.concurrent.TimeUnit;
 
 /**
  * Service for operations requiring the Bukkit API, such as for scheduling.
@@ -46,35 +41,13 @@ public class BukkitService implements SettingsDependent {
     private Method getOnlinePlayers;
     private boolean useAsyncTasks;
 
-    // Async executor
-    private ThreadPoolExecutor asyncExecutor;
-
     @Inject
     BukkitService(AuthMe authMe, Settings settings) {
         this.authMe = authMe;
         getOnlinePlayersIsCollection = initializeOnlinePlayersIsCollectionField();
-
-        int coreCount = Utils.getCoreCount();
-        // Keep 1 free core for the main thread and the OS
-        if(coreCount != 1) {
-            coreCount--;
-        }
-        asyncExecutor = new ThreadPoolExecutor(coreCount, Integer.MAX_VALUE, 60L, TimeUnit.SECONDS,
-            new SynchronousQueue<>());
-
         reload(settings);
     }
 
-    /**
-     * Wait the shutdown of the async execution pool.
-     *
-     * @throws InterruptedException if the shutdown is interrupted
-     */
-    public void closeAsyncPool() throws InterruptedException {
-        asyncExecutor.shutdown();
-        asyncExecutor.awaitTermination(30, TimeUnit.SECONDS);
-    }
-
     /**
      * Schedules a once off task to occur as soon as possible.
      * <p>
@@ -162,12 +135,12 @@ public class BukkitService implements SettingsDependent {
      * Returns a task that will run asynchronously.
      *
      * @param task the task to be run
+     * @return a BukkitTask that contains the id number
      * @throws IllegalArgumentException if plugin is null
      * @throws IllegalArgumentException if task is null
      */
-    public void runTaskAsynchronously(Runnable task) {
-        asyncExecutor.execute(task);
-        //Bukkit.getScheduler().runTaskAsynchronously(authMe, task);
+    public BukkitTask runTaskAsynchronously(Runnable task) {
+        return Bukkit.getScheduler().runTaskAsynchronously(authMe, task);
     }
 
     /**