Unnecessary volume_api.get(context, volume_id) calls

[Vincent Hou]

In methods like def delete(self, req, volume_id, id) in cinder/api/v2/volume_metadata.py, volume_api.get(context, volume_id) is called twice. The first is to get the metadata and the second is to get the volume. This can be combined into one call.

Background: I identified some critical issues and unreasonable code behaviors during my test of volume migration. My initial plan was to fix them in my blueprint of volume migration improvement. However, there is only one week left for the feature acceptance and some of my major patches may not make into master in L release, so I decide to log these issues on by one and get them fixed as soon as possible in L release.
@mtanimo, @jbernard, and @every migration contributor, some of your undergoing patches may cover these issues, but as I claimed above, major feature patches may miss the deadline of L release. Feel free to reach out to me for any migration issues. Thank you for your support.
@Every Cinder contributor, thank you for you understanding.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/218781

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/218781
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=1d1695838d4291e92043a31893d8cb103a26f627
Submitter: Jenkins
Branch: master

commit 1d1695838d4291e92043a31893d8cb103a26f627
Author: Vincent Hou <email address hidden>
Date: Mon Aug 31 17:23:48 2015 +0800

    Remove the unnecassary volume_api.get(context, volume_id)

    In the method delete from volume_image_metadata, volume_api.get()
    may be called twice. This first time is to get the metadata, and
    the second is to get the volume. We can get both of them at the
    same time.

    Change-Id: I0633c16db21e254ec43bad472748cbc0b7796a24
    Closes-Bug: #1489342