Add support for auto device selection in the attach volume screen

[Yehia Beyh]

Currently when attaching a device to an instance, the page requires a device path (ie. /dev/vdc) to be provided. This approach is error prone and creates all kinds of contusion. Especially the device you choose does not always get created, since the virtual host is the one that will select the device.

using nova volume-attach command you can use the auto option (very useful) or you can specify the device to be NULL for the api. Horizon is behind and needs to add the auto device path select.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/109356

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/109356
Committed: https://git.openstack.org/cgit/openstack/horizon/commit/?id=f60ea0abab74cbc8578addfb1bb63f4229bb2edf
Submitter: Jenkins
Branch: master

commit f60ea0abab74cbc8578addfb1bb63f4229bb2edf
Author: Mingyan Bao <email address hidden>
Date: Fri Jul 18 12:53:41 2014 -0400

    Allow auto device name for attach volume.

    The current horizon dashboard dialog for attaching a volume does not support the
    auto device name option that the cinder CLI supports. This change fixes that.

    Change-Id: If3627386a4d156d49849410ceeeddd38ce7bb933
    Closes-Bug: #1343492