Mark all running backups as FAILED when instance was deleted

Reasons:
 - users are able to delete instance while it's in BACKUP state
   and all running backups are hanging in NEW state
   and cannot be deleted;

Changes:
 - when `instance-delete` action called, all running backup
   are being marked as FAILED;
 - int-tests proposed.

Change-Id: I53d13eaa81d368864c0a278c557c7f11a509e3ea
Closes-Bug: #1220989