Change users being updated async and refactor update task

common/src/main/java/me/lucko/luckperms/runnables/UpdateTask.java

@@ -0,0 +1,24 @@
+package me.lucko.luckperms.runnables;
+
+import lombok.AllArgsConstructor;
+import me.lucko.luckperms.LuckPermsPlugin;
+
+@AllArgsConstructor
+public class UpdateTask implements Runnable {
+    private final LuckPermsPlugin plugin;
+
+    @Override
+    public void run() {
+        plugin.getLogger().info("Running update task.");
+
+        // Reload all of the groups
+        plugin.getDatastore().loadAllGroups();
+        String defaultGroup = plugin.getConfiguration().getDefaultGroupName();
+        if (!plugin.getGroupManager().isLoaded(defaultGroup)) {
+            plugin.getDatastore().createAndLoadGroup(defaultGroup);
+        }
+
+        // Refresh all online users.
+        plugin.getUserManager().updateAllUsers();
+    }
+}