Description of problem:
Today image delete operation is an async task.
If this task fails then there will be a recovery step which would try again to delete.  If the second delete fails as well then garbage is left on the domain

On block domains, delete might include a "zeroing" step for the data in case the image contains sensitive information in which case the delete operation might take a very long time (zeroing dozens of GBs or more).

To address these issues, the delete task tags the volumes to be deleted today.
What is missing is:
1. removing the "recovery step" above
2. upon startup, SPM should search the domain for volumes to delete and start deleting them.  Need to consider if deletion should be done in the context of a regular task to provide visibility to management.
In any event, need to make sure that management can list the existing volumes today including volumes that are tagged for delete so that user could decide to simply delete an unclaimed volume even without zeroing data (need to make sure to warn the user in such a case, but that is GUI logic).