[cinder][tooz]Lock-files are remained

Hi,

I'm using Queens cinder with the following setting.

--------------------------------- [coordination] backend_url = file://$state_path ---------------------------------

As a result, the files like the following were remained under the state path after some operations.[1]

cinder-63dacb3d-bd4d-42bb-88fe-6e4180164765-delete_volume cinder-32c426af-82b4-41de-b637-7d76fed69e83-delete_snapshot

In my understanding, these are lock-files created for synchronization by tooz. But, these lock-files were not deleted after finishing operations. Is this behaviour correct?

[1] e.g. Delete volume, Delete snapshot