Auto-assign replacement VM upon reimage failure

When an assigned VM fails a reimage (including where a Reimage ends "Completed" in "Mode: Cleanup" such that the VM disappears from the pool), the system should automatically replace it by assigning an unassigned VM for that user. This would provide a better user experience by helping to ensure the user has a running VM with all assigned applications installed when they log in the next day. There should be an option for admins to be notified of such an occurrence in case any manual action is required.