Comment 8 for bug 1825018

Reviewed: https://review.opendev.org/697505
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=179b556a5bebb8c5810b6065cd992a0a81bf288c
Submitter: Zuul
Branch: stable/rocky

commit 179b556a5bebb8c5810b6065cd992a0a81bf288c
Author: Matt Riedemann <email address hidden>
Date: Tue Dec 3 10:54:29 2019 -0500

    Cache security group driver

    Change I0932c652fb455fe10239215a93e183ea947234e3 from Mitaka
    was a performance improvement to cache the loaded security
    group driver since the API calls get_openstack_security_group_driver
    a lot. That performance fix was regressed with change
    Ia4a8d9954bf456253101b936f8b4ff513aaa73b2 in Newton.

    This caches the loaded security group driver once again. This
    is pretty similar to the original change except simpler since
    we don't have to account for the skip_policy_check flag.

    Change-Id: Icacc763f19db6dc90e72af32e17d480775ad5edf
    Closes-Bug: #1825018
    (cherry picked from commit 0461921d9e5313c3e92b039b90f713ed961e20c8)
    (cherry picked from commit 3ea6a7f79b0ad8a12c8ccfdeda838784c7922e63)
    (cherry picked from commit 99048af872743638b3628555e96351e00bf1eb7e)