CinderFixture: Return a driver_type of fake within connection_info

Previously the attachment info returned by the fixture would incorrectly
list the driver_type outside of the connection_info dict [1][2]. This
changes moves it within the connection_info dict and updates the type to
`fake` for use by the libvirt driver that provides a compatible volume
driver [3] for use in our functional tests.

[1] https://docs.openstack.org/api-ref/block-storage/v3/index.html?expanded=create-attachment-detail#id407
[2] https://docs.openstack.org/api-ref/block-storage/v3/index.html?expanded=update-an-attachment-detail#id411
[3] https://github.com/openstack/nova/blob/2c3ff1004e8812da0bc4e5502762e6b9a7650846/nova/virt/libvirt/volume/volume.py#L171-L184

Change-Id: I73ff0a7508d9f8f6f3d498be13f6f7c505b05e5c

Author: lyarwood

nova/tests/fixtures.py

@@ -2575,11 +2575,16 @@ def fake_attachment_update(_self, context, attachment_id, connector,
                             _attachment['connector'].get('host')))
             attachment['connector'] = connector
             LOG.info('Updating volume attachment: %s', attachment_id)
-            attachment_ref = {'driver_volume_type': 'fake_type',
-                              'id': attachment_id,
-                              'connection_info': {'data':
-                                                  {'foo': 'bar',
-                                                   'target_lun': '1'}}}
+            attachment_ref = {
+                'id': attachment_id,
+                'connection_info': {
+                    'driver_volume_type': 'fake',
+                    'data': {
+                        'foo': 'bar',
+                        'target_lun': '1'
+                    }
+                }
+            }
             if attachment_id == self.SWAP_ERR_ATTACH_ID:
                 # This intentionally triggers a TypeError for the
                 # instance.volume_swap.error versioned notification tests.