Short-circuit notifications when not enabled

[chenying]

In Mitaka oslo messaging introduced the transport_url specific for
notifications under the oslo_messaging_notifications section, but some
projects still use the default transport_url defined in the DEFAULT
section. Use messaging notifications transport instead of default.

This patch proposes short-circuiting notification methods as much as
possible to optimize code execution when Karbor has no notification
transport mechanism configured.

The NOTIFIER only be inited only if notifications are actually enabled.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/507757
Committed: https://git.openstack.org/cgit/openstack/karbor/commit/?id=2f529a62bf64555e004364d027be0bd5a1781181
Submitter: Jenkins
Branch: master

commit 2f529a62bf64555e004364d027be0bd5a1781181
Author: chenying <email address hidden>
Date: Wed Sep 27 14:54:28 2017 +0800

    Short-circuit notifications when not enabled

    In Mitaka oslo messaging introduced the transport_url specific for
    notifications under the oslo_messaging_notifications section, but some
    projects still use the default transport_url defined in the DEFAULT
    section. Use messaging notifications transport instead of default.

    This patch proposes short-circuiting notification methods as much as
    possible to optimize code execution when Karbor has no notification
    transport mechanism configured.

    The NOTIFIER only be inited only if notifications are actually
    enabled.

    Change-Id: Id9419ddd801bf9d8ac13c4a73a91e39fd763cb2b
    Closes-Bug: #1719786

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/karbor 0.6.0 release.

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/karbor 1.0.0 release.

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/karbor 1.1.0 release.