os-brick does not provide CHAP credentials for discovery

[Jose Porrua]

It looks like the changes made to some of the libvirt volume drivers to use os-brick left out the code that provided credentials to discover devices (introduced by change-id : I400db60fcc29c2d5e2d3b9dabc055649138468eb)

The change is straightforward so I made some changes to the code and am currently testing it.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/212191

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/212191
Committed: https://git.openstack.org/cgit/openstack/os-brick/commit/?id=2ff5d8edca2edcb3da278fee8f5e8066e83b3d0e
Submitter: Jenkins
Branch: master

commit 2ff5d8edca2edcb3da278fee8f5e8066e83b3d0e
Author: Jose Porrua <email address hidden>
Date: Thu Aug 6 13:45:55 2015 -0400

    Adding CHAP discovery logic to os-brick

    The changes that were made to libvirt volume drivers to use
    os-brick, left out the code that provided credentials to discover
    iSCSI devices

    Essentially, the code responsible for updating iscsiadm's CHAP
    authentication parameters was left out

    Closes-Bug: #1481914

    Change-Id: I3fa0132247374d89b9fdcfdba3e9b1eac502a2ad