Block player logins during server shutdown

Adds GH-765

Spigot-Server-Patches/Block-player-logins-during-server-shutdown.patch

@@ -0,0 +1,23 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Zach Brown <1254957+zachbr@users.noreply.github.com>
+Date: Sun, 2 Jul 2017 21:35:56 -0500
+Subject: [PATCH] Block player logins during server shutdown
+
+
+diff --git a/src/main/java/net/minecraft/server/LoginListener.java b/src/main/java/net/minecraft/server/LoginListener.java
+index 2158fcd3..2367023c 100644
+--- a/src/main/java/net/minecraft/server/LoginListener.java
++++ b/src/main/java/net/minecraft/server/LoginListener.java
+@@ -0,0 +0,0 @@ public class LoginListener implements PacketLoginInListener, ITickable {
+     }
+ 
+     public void e() {
++        // Paper start - Do not allow logins while the server is shutting down
++        if (!MinecraftServer.getServer().isRunning()) {
++            this.disconnect(new ChatMessage(org.spigotmc.SpigotConfig.restartMessage));
++        }
++        // Paper end
+         if (this.g == LoginListener.EnumProtocolState.READY_TO_ACCEPT) {
+             this.b();
+         } else if (this.g == LoginListener.EnumProtocolState.DELAY_ACCEPT) {
+--