Remember which comments we imported and don't import them a second

time.  Fixes ticket #1282.

modules/g2_import/helpers/g2_import.php

@@ -845,6 +845,11 @@ static function import_comment(&$queue) {
                array("id" => $g2_comment_id, "exception" => (string)$e));
     }
 
+    if (self::map($g2_comment->getId())) {
+      // Already imported
+      return;
+    }
+
     $item_id = self::map($g2_comment->getParentId());
     if (empty($item_id)) {
       // Item was not mapped.
@@ -877,6 +882,8 @@ static function import_comment(&$queue) {
           $e);
     }
 
+    self::set_map($g2_comment->getId(), $comment->id, "comment");
+
     // Backdate the creation date.  We can't do this at creation time because
     // Comment_Model::save() will override it.
     db::update("comments")