Comment 7 for bug 1461055

One more clue, out of my two compute nodes total of 66 instances.
4 instances are stuck in task_state deleting.
6 have a status of deleted, yet remain with task_state "-"
All of them reside on the same compute node.

Restarting nova service on the effected compute node removed all phantom instances.
But this isn't a solution only a temp workaround.