db call to snapshot_update doesn't return an updated ref

[John Griffith]

When doing a snapshot_update call to the DB we don't currently return an updated ref. Instead, we've been working on the premise that the caller would then do a second api call to get a new ref. We should short circuit this and just return the updated reference. This also aligns with how the update_volume call works.

There may be other update calls that need this work as well.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/110334

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/110334
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=e4ad50563cc594f2648b1714039105d9bb3f4e7d
Submitter: Jenkins
Branch: master

commit e4ad50563cc594f2648b1714039105d9bb3f4e7d
Author: John Griffith <email address hidden>
Date: Tue Jul 29 09:41:06 2014 -0600

    Add return of updated object on update from DB

    There are a number of update methods in db/sqla/api
    that update objects but no longer return the updated
    reference for said object.

    This patch adds the missing returns which are already
    expected in the calling cidner/db/api wrapper. At some
    point a close look at usage in callers
    (ie cinder/volume/manager) should be done to make sure
    we're being efficient here and not doing another get after
    every update.

    Change-Id: I0464d1879571a0044a416d652a186b1462c57fa2
    Closes-Bug: #1349912