GPFS Driver should implement clone_image for efficient volume creation

[Bill Owen]

Modify GPFS driver organization so that the code for dealing with moving image files from gpfs-backed glance repository to gpfs-backed volumes resides in clone_image function. This simplifies the code and better follows the intent of the clone_image function.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/42446

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/42446
Committed: http://github.com/openstack/cinder/commit/5f5a37d31a4466e32fad39000ecf71156cc09b2d
Submitter: Jenkins
Branch: master

commit 5f5a37d31a4466e32fad39000ecf71156cc09b2d
Author: Bill Owen <email address hidden>
Date: Fri Aug 16 15:49:06 2013 -0700

    GPFS use clone_image for creating volumes

    If both source and target of gpfs create volume from image operation
    are backed by gpfs storage use clone_image method for implementing
    the move of image data to the new volume.

    The copy_image_to_volume method is used only if this is not true,
    and uses image_utils.fetch_to_raw to move image data to the new
    volume.

    Fixes bug #1213248

    Change-Id: I3958febe67cc86bc3cb608288f7d064f74d3a731