Do not use worldgen executor for api profile completions

We cannot put blocking network I/O onto the worldgen threads,
this will crash the server if it stalls

patches/server/0139-Add-UnknownCommandEvent.patch

@@ -0,0 +1,25 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Sweepyoface <github@sweepy.pw>
+Date: Sat, 17 Jun 2017 18:48:21 -0400
+Subject: [PATCH] Add UnknownCommandEvent
+
+
+diff --git a/src/main/java/org/bukkit/craftbukkit/CraftServer.java b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
+index 20d1fafc33f207f5e922df9fa5e152e003717a1c..c55a18eadc2bef0c98abd46898e10a5110212c68 100644
+--- a/src/main/java/org/bukkit/craftbukkit/CraftServer.java
++++ b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
+@@ -888,7 +888,13 @@ public final class CraftServer implements Server {
+ 
+         // Spigot start
+         if (!org.spigotmc.SpigotConfig.unknownCommandMessage.isEmpty()) {
+-            sender.sendMessage(org.spigotmc.SpigotConfig.unknownCommandMessage);
++            // Paper start
++            org.bukkit.event.command.UnknownCommandEvent event = new org.bukkit.event.command.UnknownCommandEvent(sender, commandLine, org.spigotmc.SpigotConfig.unknownCommandMessage);
++            Bukkit.getServer().getPluginManager().callEvent(event);
++            if (event.message() != null) {
++                sender.sendMessage(event.message());
++            }
++            // Paper end
+         }
+         // Spigot end
+