Removing, umount and detaching loop device doesn't clear the btrfs.list 

## Scenario
1-  Do `client.btrfs.device_remove`
2- umount and detach the loop device 

## Actual Result
3- List btrfs filesystems using `client.btrfs.list()`, the btrfs filesystem is still there

## Expected result
The btrfs filesystem should be removed
