Security scanner ordered tuplize bug fix

If only the old list is present, we still need to tuplize the entries.

Fixes https://sentry.io/coreos/backend-production/issues/207196561/

util/secscan/notifier.py

@@ -112,7 +112,9 @@ class SecurityNotificationHandler(object):
     # Check for ordered data. If found, we use the indexed tracker, which is faster and
     # more memory efficient.
     is_indexed = False
-    if 'OrderedLayersIntroducingVulnerability' in new_data:
+    if ('OrderedLayersIntroducingVulnerability' in new_data or
+        'OrderedLayersIntroducingVulnerability' in old_data):
+
       def tuplize(stream):
         return [(entry['LayerName'], entry['Index']) for entry in stream]