Comment 2 for bug 1507504

Reviewed: https://review.fuel-infra.org/12911
Submitter: Vitaly Sedelnik <email address hidden>
Branch: openstack-ci/fuel-6.1/2014.2

Commit: cbf71d63b8bb658c0bbf20cc34ced6e08d48ff68
Author: StephenSun <email address hidden>
Date: Tue Oct 20 10:33:12 2015

libvirt: fix disk I/O QOS support with RBD

The disk I/O QOS settings were set in the libvirt_info
method of the Image class. While this is fine for most
subclasses, the Rbd subclass overrides this method and
so was loosing the QOS settings. Move the setting of
QOS parameters into a separate method so it can be
called in all places that need it. For added fun the
commit 86e6f34 which added QOS settings originally never
added any unit tests to cover its operation.

Conflicts:
        nova/tests/unit/virt/libvirt/test_imagebackend.py

Co-authored: Daniel P. Berrange <email address hidden>
Closes-Bug: #1507504
Change-Id: Ibb3a4dff8996c29ef921be7c56648a442bbb89a2
(cherry picked from commit fdb7b030abbff85d19581c3f2b0ba68683fd8d6f)