Comment 4 for bug 1901302

Reviewed: https://review.opendev.org/759566
Committed: https://git.openstack.org/cgit/openstack/tripleo-validations/commit/?id=83411f3f603a8e4379f72fac23fdead107c2f1df
Submitter: Zuul
Branch: stable/train

commit 83411f3f603a8e4379f72fac23fdead107c2f1df
Author: Alexey Stupnikov <email address hidden>
Date: Sat Oct 24 13:24:58 2020 +0200

    [train and before] Define default firewall_driver value

    no-op-firewall-nova-driver validation fails if firewall_driver is
    not defined in nova.conf. At the same time, default definition is
    also OK and validation should pass if firewall_driver is not
    defined.

    The no-op-firewall-nova-driver validation was removed during Ussuri
    cycle[1] so this change is submitted to train and older branches

    [1] f1963a4e8396c9b833619e57d4b9509af887c2b0

    Closes-Bug: #1901302
    Related: rhbz#1891204
    Change-Id: I5bf05356bc2bda6ede2df6f7688c2c5e2f46f20e