pylint warnings in nova.virt.block_device

[Mark McLoughlin]

See https://review.openstack.org/#/c/39086/24/nova/virt/block_device.py

 nova/virt/block_device.py:49: [E1101, DriverBlockDevice.__init__] Instance of 'DriverBlockDevice' has no '_fields' member
nova/virt/block_device.py:62: [E1101, DriverBlockDevice.legacy] Instance of 'DriverBlockDevice' has no '_legacy_fields' member

The base class should have these members too

[Davanum Srinivas (DIMS) (dims-v)]

https://review.openstack.org/#/c/54819/

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/54819
Committed: http://github.com/openstack/nova/commit/5647c6f4579b1a6d715c131e49484b72f9bca4be
Submitter: Jenkins
Branch: master

commit 5647c6f4579b1a6d715c131e49484b72f9bca4be
Author: Davanum Srinivas <email address hidden>
Date: Thu Oct 31 16:06:03 2013 -0400

    Add missing fields in DriverBlockDevice

    Pylint reports the following, let's clean them up
    ["Instance of 'DriverBlockDevice' has no '_fields' member", ""]
    ["Instance of 'DriverBlockDevice' has no '_legacy_fields' member", ""]

    Change-Id: Iaf56dc35ce5ad963a6fb50d6641b203409ca6798
    Closes-Bug: #1214377