Don't run tasks when the server is stopping

nms-patches/MinecraftServer.patch

@@ -1,5 +1,5 @@
---- /home/matt/mc-dev-private//net/minecraft/server/MinecraftServer.java	2015-03-08 10:08:09.275589093 +0000
-+++ src/main/java/net/minecraft/server/MinecraftServer.java	2015-03-08 10:08:09.279589093 +0000
+--- /home/matt/mc-dev-private//net/minecraft/server/MinecraftServer.java	2015-03-11 10:44:42.911576345 +0000
++++ src/main/java/net/minecraft/server/MinecraftServer.java	2015-03-11 10:44:42.915576345 +0000
 @@ -38,14 +38,27 @@
  import org.apache.logging.log4j.LogManager;
  import org.apache.logging.log4j.Logger;
@@ -678,3 +678,12 @@
      }
  
      public void a(CommandObjectiveExecutor.EnumCommandResult commandobjectiveexecutor_enumcommandresult, int i) {}
+@@ -1180,7 +1411,7 @@
+ 
+     public <V> ListenableFuture<V> a(Callable<V> callable) {
+         Validate.notNull(callable);
+-        if (!this.isMainThread() && !this.isStopped()) {
++        if (!this.isMainThread()) { // CraftBukkit && !this.isStopped()) {
+             ListenableFutureTask listenablefuturetask = ListenableFutureTask.create(callable);
+             Queue queue = this.j;
+