management: Add lockfiles to all _once management jobs.

These would be bad if more than once ran at once.

zerver/management/commands/delete_old_unclaimed_attachments.py

@@ -8,6 +8,7 @@ from typing_extensions import override
 
 from zerver.actions.uploads import do_delete_old_unclaimed_attachments
 from zerver.lib.attachments import get_old_unclaimed_attachments
+from zerver.lib.management import abort_unless_locked
 from zerver.lib.upload import all_message_attachments, delete_message_attachments
 from zerver.models import ArchivedAttachment, Attachment
 
@@ -44,6 +45,7 @@ class Command(BaseCommand):
         )
 
     @override
+    @abort_unless_locked
     def handle(self, *args: Any, **options: Any) -> None:
         delta_weeks = options["delta_weeks"]
         print(f"Deleting unclaimed attached files older than {delta_weeks} weeks")