Description of problem:

When snapshot deletion fails because engine was restarted in the middle of deletion process the task never stops running. Getting exceptions in engine and  snapshot names that user sees in the Events Log presented as  "UNKNOWN" 

here is the engine log.
It's a race ,reproduces not 100%.
Version-Release number of selected component (if applicable):


How reproducible:

how to reproduce:
1.Create VM with disks.
2.Create snapshot.
2.Delete snapshot. Make the deletion fail. (restart engine while deleting snapshot).

logs attached.