Missing implementation to get, delete, and update volume metadata

[Thang Pham]

There are four methods in nova/nova/volume/cinder.py which are NotImplemented. They are as follows:
1. get_volume_metadata
2. delete_volume_metadata
3. update_volume_metadata
4. get_volume_metadata_value

These methods are required in cases where nova needs to modify a cinder volume's metadata, e.g. attach and detach time.

The latest code in nova's master branch shows these methods as NotImplemented.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/82411

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/82411
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=46d8dcfa5807ef84d6b96b056957a1b9aa0daff7
Submitter: Jenkins
Branch: master

commit 46d8dcfa5807ef84d6b96b056957a1b9aa0daff7
Author: Thang Pham <email address hidden>
Date: Sun Mar 23 21:33:43 2014 -0400

    Implement methods to modify volume metadata.

    There are four methods in nova/volume/cinder.py which are
    NotImplemented. They are as follows:
      1. get_volume_metadata
      2. delete_volume_metadata
      3. update_volume_metadata
      4. get_volume_metadata_value
    These methods are required in cases where nova needs to modify
    a cinder volume's metadata, e.g. attach and detach time. It also
    completes the cinder.API class.

    Change-Id: I360076ae28db43e661466f556425947813c9040e
    Closes-Bug: #1296164