fix failed sanitise flow

the move from virus scan to validation failed function was called with
the wrong variables, and had some internal logic that was slightly
wrong.

Also, Don't use `update_notification_by_id` for notifications if they
are not in `created`, `sending`, `pending`, or `sent`. It silently
doesn't update them. I didn't want to do a deeper investigation into
the reasons behind this terrifying state machine as part of this commit
so I just changed the functions to call `dao_update_notification`
manually

app/celery/letters_pdf_tasks.py

@@ -27,8 +27,9 @@ from app.letters.utils import (
     get_reference_from_filename,
     get_folder_name,
     upload_letter_pdf,
-    move_failed_pdf,
     ScanErrorType,
+    move_failed_pdf,
+    move_scan_to_invalid_pdf_bucket,
     move_error_pdf_to_scan_bucket,
     get_file_names_from_error_bucket
 )
@@ -41,8 +42,6 @@ from app.models import (
     NOTIFICATION_VALIDATION_FAILED
 )
 
-from app.letters.utils import move_scan_to_invalid_pdf_bucket
-
 
 @notify_celery.task(bind=True, name="create-letters-pdf", max_retries=15, default_retry_delay=300)
 @statsd(namespace="tasks")
@@ -194,8 +193,11 @@ def process_virus_scan_passed(self, filename):
 
     if not new_pdf:
         current_app.logger.info('Invalid precompiled pdf received {} ({})'.format(notification.id, filename))
-        update_notification_status_by_id(notification.id, NOTIFICATION_VALIDATION_FAILED)
-        move_scan_to_invalid_pdf_bucket(scan_pdf_object)
+
+        notification.status = NOTIFICATION_VALIDATION_FAILED
+        dao_update_notification(notification)
+
+        move_scan_to_invalid_pdf_bucket(filename)
         scan_pdf_object.delete()
         return
     else:
@@ -257,7 +259,9 @@ def _sanitise_precomiled_pdf(self, notification, precompiled_pdf):
             current_app.logger.exception(
                 "RETRY FAILED: sanitise_precomiled_pdf failed for notification {}".format(notification.id),
             )
-            update_notification_status_by_id(notification.id, NOTIFICATION_TECHNICAL_FAILURE)
+
+            notification.status = NOTIFICATION_TECHNICAL_FAILURE
+            dao_update_notification(notification)
             raise