Cleanup after plugins which don't sucessfully enable

This change closes the plugin via the plugin manager, which disables
the plugin, as intended, but also cleans up after the plugin, preventing
any further errors or issues caused by tasks scheduled by the plugin before
it failed.

Backport of 1.13 cf772531f4

Spigot-API-Patches/0103-Close-Plugin-Class-Loaders-on-Disable.patch

@@ -1,4 +1,4 @@
-From 13d2ed50d6346f5c8eb7833dd99f7c61e8fd0b29 Mon Sep 17 00:00:00 2001
+From 8b9f3c48dcc40317ca51b6138eb6e3b766a8652c Mon Sep 17 00:00:00 2001
 From: Aikar <aikar@aikar.co>
 Date: Tue, 1 May 2018 21:33:35 -0400
 Subject: [PATCH] Close Plugin Class Loaders on Disable
@@ -100,7 +100,7 @@ index bd0588a2..cb2b0b9c 100644
              lookupNames.clear();
              HandlerList.unregisterAll();
 diff --git a/src/main/java/org/bukkit/plugin/java/JavaPluginLoader.java b/src/main/java/org/bukkit/plugin/java/JavaPluginLoader.java
-index 40fd71dc..3e87c3dd 100644
+index 40fd71dc..8b5cea64 100644
 --- a/src/main/java/org/bukkit/plugin/java/JavaPluginLoader.java
 +++ b/src/main/java/org/bukkit/plugin/java/JavaPluginLoader.java
 @@ -317,7 +317,7 @@ public final class JavaPluginLoader implements PluginLoader {
@@ -108,7 +108,7 @@ index 40fd71dc..3e87c3dd 100644
                  server.getLogger().log(Level.SEVERE, "Error occurred while enabling " + plugin.getDescription().getFullName() + " (Is it up to date?)", ex);
                  // Paper start - Disable plugins that fail to load
 -                disablePlugin(jPlugin);
-+                disablePlugin(jPlugin, true); // Paper - close Classloader on disable - She's dead jim
++                server.getPluginManager().disablePlugin(jPlugin, true); // Paper - close Classloader on disable - She's dead jim
                  return;
                  // Paper end
              }
@@ -144,5 +144,5 @@ index 40fd71dc..3e87c3dd 100644
          }
      }
 -- 
-2.17.1
+2.19.2