Mark imports as complete

This will let the user debug the import, and should only be used when
the import is in a bad state (marked as incomplete but with no pending
tasks)

bookwyrm/models/import_job.py

@@ -53,6 +53,7 @@ class ImportJob(models.Model):
         """How many books do you want to import???"""
         return self.items.count()
 
+    @property
     def pending_item_count(self):
         """And how many pending items??"""
         return self.pending_items.count()