Replace passing system_metadata to notification functions with instance.system_metadata usage

[Balazs Gibizer]

Both notify_usage_exists() [1] and info_from_instance() [2] functions used in the notification code path get the system_metadata passed in. Instead we should use the instance.system_metadata directly whenever it is possible.

[1] https://github.com/openstack/nova/blob/57d3b7093259b625672a98b0ff41643175f6cb82/nova/compute/utils.py#L278
[2]https://github.com/openstack/nova/blob/57d3b7093259b625672a98b0ff41643175f6cb82/nova/notifications/base.py#L382

[Matt Riedemann (mriedem)]

Looking at https://github.com/openstack/nova/blob/57d3b7093259b625672a98b0ff41643175f6cb82/nova/compute/utils.py#L278 it looks like it is used in the case of rebuild:

https://github.com/openstack/nova/blob/57d3b7093259b625672a98b0ff41643175f6cb82/nova/compute/manager.py#L3034

Which comes from conductor:

https://github.com/openstack/nova/blob/57d3b7093259b625672a98b0ff41643175f6cb82/nova/conductor/manager.py#L982

Which comes from the API:

https://github.com/openstack/nova/blob/57d3b7093259b625672a98b0ff41643175f6cb82/nova/compute/api.py#L3080

In case the system_metadata changes because of a new image and it's properties...so I guess we should just remove the comment about being used in the docstring for notify_usage_exists().

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/561724

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/561724
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=1c36654ad8eadfa4e0fca785b1a8a717de118b50
Submitter: Zuul
Branch: master

commit 1c36654ad8eadfa4e0fca785b1a8a717de118b50
Author: Matt Riedemann <email address hidden>
Date: Mon Apr 16 16:58:07 2018 -0400

    Remove vestigial system_metadata param from info_from_instance()

    The system_metadata argument to info_from_instance() was not used
    so it's removed in this change, along with all callers of that
    method, which goes quite a ways.

    Also, the docstring for the system_metadata argument to
    notify_usage_exists() is updated since it is passed in one
    specific place: rebuild with a new image. In that case, nova-api
    saves off the original instance system_metadata before resetting
    the system_metadata based on the new image to rebuild, which is
    then passed down through nova-conductor and nova-compute where
    it eventually gets used to override "image_meta" in the payload
    created in info_from_instance(). It's weird, yes, and essentially
    means that for legacy versioned notifications, the instance payload
    will always contain the image_meta for the instance before it's
    rebuilt with the new image, which is something we don't do for
    versioned notifications.

    Test test_local_delete_without_info_cache is removed since it's
    (1) weird in that it is doing mox-like stuff in a mock-based
    test and (2) the code it was meant to test from change
    Ie0bba032615d3da06cdd95b221beb37a9b8a377d no longer exists.

    Change-Id: Ia1820334dcaceca9d7fa874dd7c553fa1c5befec
    Closes-Bug: #1764390

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/nova 18.0.0.0b2 development milestone.