If an instance gets stuck in an intermediate state (e.g., "deleting"), you can manually reset the state of an instance using the nova reset-state command. This will reset it to an error state, which you can then delete. For example:
$ nova reset-state c6bbbf26-b40a-47e7-8d5c-eb17bf65c485 $ nova delete c6bbbf26-b40a-47e7-8d5c-eb17bf65c485
You can also use the --active to force the instance back into
an active state instead of an error state, for example:
$ nova reset-state --active c6bbbf26-b40a-47e7-8d5c-eb17bf65c485
