Object obj_extra_fields not properly used

[Thang Pham]

Fields that are not part of the Snapshot model, i.e. name and volume_name, should be specified in obj_extra_fields in the object.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/165214

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/165214
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=2d7d86fccd0923ac17f55431cf756f980a5abc9c
Submitter: Jenkins
Branch: master

commit 2d7d86fccd0923ac17f55431cf756f980a5abc9c
Author: Thang Pham <email address hidden>
Date: Tue Mar 17 10:24:08 2015 -0400

    Properly use obj_extra_fields in objects

    The following patch fixes a bug in the snapshot object,
    where fields that are not part of the Snapshot model,
    i.e. name and volume_name, were not specified as
    obj_extra_fields in the object. It also fixes the same
    problem in the volume object, i.e. name and name_id.
    With this patch, those extra fields are properly loaded,
    e.g. snapshot.volume_name or volume.name.

    Change-Id: Ie2b8dc66c897f89f941e9ad3b80ec4f4ab346430
    Closes-Bug: #1429889