Use plugins repo version of the human_log callback plugin
Use plugins repo version of the human_log callback plugin

With the implementation of https://review.openstack.org/321331 the
human_log callback plugin is now part of the plugins repo.

This patch removes the retrofitted version in tox in favor of using
the version from the plugins repo instead.

Change-Id: Ied88dd355c41e48566c6179333930d625dc9637c

openstack/openstack-ansible-lxc_container_create,Logan2211/openstack-ansible-lxc_container_create,openstack/openstack-ansible-lxc_container_create,Logan2211/openstack-ansible-lxc_container_create