Feature Request Overview (mandatory - Complete while in New status){_}
{}What user goal or problem do you need to solve?{_} 

The current volume revert operation has improvement points.

1. User needs to delete an instance when the boot volume is the target device is volume revert operation.
2. Even if non-bootable volume, the user needs to stop the instance manually.

This is a little bit annoying operation compared to VMware or else.

The improved operation will look like:
When a user requests volume revert,
1. Stop the instance if it is running and lock from any operations in nova.
2. Revert the volume even if the volume is bootable volume.
3. Remove the lock in nova and stay the instance is stopped after the volume revert is completed.

Business justification (mandatory - Complete while in New status)
How would this feature benefit the customer?
The current volume revert operation for boot volume requires deleting an instance.
It is not ideal operation and the user needs to preserve IP address or anything else for the operation. 
Also, there are no lock mechanism while volume revert in nova.

Functional requirements (mandatory - Complete while in New status){_}
{}What do you want the result of this feature to be? Add as many requirements as needed.{_}
When a user requests volume revert,
1. Stop the instance if it is running and lock from any operations in nova.
2. Revert the volume even if the volume is bootable volume.
3. Remove the lock in nova and stay the instance is stopped after the volume revert is completed.

Describe the customer impact
The current volume revert operation with bootable volume requires many works and it change the instance state like port UUID and instance UUID because it requires deleting an instance.

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