Comment 4 for bug 1721423

Reviewed: https://review.openstack.org/509806
Committed: https://git.openstack.org/cgit/openstack/horizon/commit/?id=6d0fb73ee044f74de85673af4265576adf749e52
Submitter: Jenkins
Branch: stable/pike

commit 6d0fb73ee044f74de85673af4265576adf749e52
Author: Feilong Wang <email address hidden>
Date: Thu Oct 5 14:37:34 2017 +1300

    Add cache for get_microversion() against Nova

    Actions "Lock" and "Unlock" of instance on instances table are calling
    api.nova.is_feature_available() to check if the feature is supported
    by current Nova server. Unfortunately, the function get_microversion()
    called by is_feature_available() is not cached, which is causing about
    40 unnecesary REST API calls. If the Nova's version is under Mitaka,
    it could be even worse, about 80 unnecesary API calls, see
    openstack_dashboard/api/nova.py#L60 and
    novaclient/v2/versions.py#L47 for more details.

    Closes-Bug: #1721423

    Change-Id: Ie96b1a35e379d4cf407bfd53b1ee734178f9cb07
    (cherry picked from commit fa2e8327b9d0a10f29a4fbe3094a4533914b8ce3)