undercloud installation adds stack user to docker group but user needs to relogin for that to work

[Michele Baldessari]

We currently do the following to add the 'stack' user on the undercloud to the 'docker' group so it can access the docker daemon (when the local docker registry option is enabled):
...
if str2bool(hiera('enable_docker_registry', true)) {
  group { 'docker':
    ensure => 'present',
  }
  user { 'docker_user':
    name => hiera('tripleo_install_user'),
    groups => 'docker',
    notify => Service['docker'],
  }
  include ::tripleo::profile::base::docker_registry
}
...

For this to work the stack user needs to logoff and logon again (or call newgrp)

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/511490

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/511490
Committed: https://git.openstack.org/cgit/openstack/tripleo-docs/commit/?id=e3b006853dbbe957eae9da2ce00ae66a4507e2c6
Submitter: Zuul
Branch: master

commit e3b006853dbbe957eae9da2ce00ae66a4507e2c6
Author: Michele Baldessari <email address hidden>
Date: Thu Oct 12 16:22:30 2017 +0200

    Add a note about relogging in as the stack user when docker commands fail

    We currently do the following to add the 'stack' user on the undercloud
    to the 'docker' group so it can access the docker daemon (when the local
    docker registry option is enabled):
    ...
    if str2bool(hiera('enable_docker_registry', true)) {
      group { 'docker':
        ensure => 'present',
      }
      user { 'docker_user':
        name => hiera('tripleo_install_user'),
        groups => 'docker',
        notify => Service['docker'],
      }
      include ::tripleo::profile::base::docker_registry
    }
    ...

    For this to work the stack user needs to logoff and logon again.
    Closes-Bug: #1722498

    Change-Id: Ia1f76f61828c119667879c41f1ad5d86b8901adb