Boot an instance from volume but failed, then delete this instance successfully, but volume is still in-use.

[Charlotte Han]

Description
===========
Boot an instance from volume failed, then delete this instance successfully, but volume is still in-use.

Steps to reproduce
==================
A chronological list of steps which will bring off the
issue you noticed:
* I did boot an instance from volume. Instance is error and instance.host is None.
* then I did delete this instance successfully. The booted volume is still in-use.
* then I did delete this volume.

But this volume is not allowed to be deleted because volume is still in-use.

Expected result
===============
This volume can be deleted successfully.
After delete instance, booted volume should be reverted to available state.

Actual result
=============
This volume is not allowed to be deleted.

Environment
===========
1. pike

2. Which hypervisor did you use?
   Libvirt + KVM

3. Which storage type did you use?
   LVM

[Ameed Ashour (ameeda)]

Hi

I think Mel resolve this issue on master https://review.openstack.org/#/c/340614/

Regards
Ameed