Unable to scrub image

[Timofey G]

Bug description:

Scrubber floods logs with error messages when deleting images having location property.

Steps to reproduce:

1) Create image with location

   glance --os-image-api-version 1 image-create --location https://<URL>

2) Delete created image

   glance image-delete <ID>

3) See logs

glance.scrubber[24081]: WARNING One or more image locations couldn't be scrubbed from backend. Leaving image '020abe69-d154-44dc-b2f8-501e1ce40ed0' in 'pending_delete' status.

glance.scrubber[24081]: ERROR Unable to scrub image 020abe69-d154-44dc-b2f8-501e1ce40ed0 from a location. Reason: Deleting images from this store is not supported.

4) Every 5 minutes this messages appear in logs. This situation continue forever.