Comment 1 for bug 1623738

Reviewed: https://review.openstack.org/290919
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=0683fcd3f551dc55438d9f8415b8931f22635bd5
Submitter: Jenkins
Branch: master

commit 0683fcd3f551dc55438d9f8415b8931f22635bd5
Author: Giridhar Jayavelu <email address hidden>
Date: Wed Mar 9 14:10:49 2016 -0800

    Handle TypeError when disabling host service

    When _set_host_enabled() in virt/libvirt/driver.py
    is called to change service status of a host from
    enabled to disabled without providing disable_reason, then
    a TypeError occurs while concatenating disabled_reason with
    DISABLE_PREFIX. This prevents the service status of the host
    from being updated.

    This patch handles the case when disable_reason is None.
    Also, unit tests have been fixed to validate the code path for
    changing the disabled state of a host.

    Closes-Bug: #1623738
    Change-Id: Ib131f73444234723ef8bbb15bb4bd4a62a83320d