Comment 6 for bug 1901732

The problem is that you've specified the volume_type options in the controller_worker section of the config file. The following options for Cinder can be specified in the [cinder] config section (though the documentation does not clearly state this, the code does). Specifying them in the [controller_worker] will not yield the results you want. The volume is likely getting created with the default volume type - which I suspect has multiattach enabled.

The correct settings would have:

[controller_worker]
...
volume_driver = volume_cinder_driver
...

[cinder]
volume_size = 16
volume_type = <volume_type>
volume_create_retry_interval = 5
volume_create_timeout = 300
volume_create_max_retries = 5