Remove unnecessary db calls made to fetch original metadata when delete flag is set to True

[Aswad Rangnekar]

Found in commit 75bcf70ed4698f0ffba4c6a7236a1e30b1214b57

Original metadata is retrieved unnecessarily from the database when delete flag is set to True in the following methods in cinder volume api.

update_volume_metadata
update_volume_admin_metadata
update_snapshot_metadata

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/54544

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/54544
Committed: http://github.com/openstack/cinder/commit/d281149ea0f860c7c862f7897710d2e1fcb681e7
Submitter: Jenkins
Branch: master

commit d281149ea0f860c7c862f7897710d2e1fcb681e7
Author: Aswad Rangnekar <email address hidden>
Date: Wed Oct 30 05:45:35 2013 -0700

    Remove unused db calls to fetch original metadata

    Remove unnecessary db calls made to fetch
    original metadata when delete flag is set
    to True.

    Closes-Bug: #1246291

    Change-Id: If7483b8b21f71efa5e7c211b031170bc03eb6b9b