Description of problem:
When a user sets "containerized=true" globally in their inventory it is applied even to host types for which we have no containerized components or any business installing Docker on via this installer: nfs / glusterfs / lb hosts. Docker is installed and the Docker checks run and report problems.


Version-Release number of the following components:
openshift3/ose-ansible:v3.6 installer image


Steps to Reproduce:
1. Create an inventory with containerized=true and some nfs/lb/glusterfs hosts.
2. Run the pre-install checks e.g.
    docker run -u `id -u`
           -v $HOME/.ssh/id_rsa:/opt/app-root/src/.ssh/id_rsa:Z,ro
           -v /etc/ansible/hosts:/tmp/inventory:ro
           -e INVENTORY_FILE=/tmp/inventory     
           -e PLAYBOOK_FILE=playbooks/byo/openshift-checks/pre-install.yml
           openshift3/ose-ansible:v3.6
3. See output and rpm -q docker on the hosts

Actual results:
Failure summary:

  1. Host:     <nfs host>
     Play:     Verify Requirements
     Task:     openshift_health_check
     Message:  One or more checks failed
     Details:  check "docker_storage":
               Use of loopback devices with the Docker devicemapper storage driver
               (the default storage configuration) is unsupported in production.
               Please use docker-storage-setup to configure a backing storage volume.
               See http://red.ht/2rNperO for further information.
# rpm -q docker
docker-1.12.6-...


Expected results:
Should not have anything to do or say about Docker on these hosts, even though they are marked containerized.

Additional info:
The obvious workaround is to update the inventory so these hosts are not set to containerized. If "containerized=true" is set globally in the [OSEv3:vars] section it can easily be overridden with an entry per-host.

Logic at https://github.com/openshift/openshift-ansible/blob/167117dc280e4448b76ac95868ca33f527383d20/roles/openshift_version/meta/main.yml#L17-L18 could be refined to include the docker role only on hosts we know could actually need Docker, regardless of what containerized says. Alternately, the logic for setting openshift.common.is_containerized could be modified. Or the docker role could exempt itself when not invoked on whitelisted host groups.

Health check logic at https://github.com/openshift/openshift-ansible/blob/167117dc280e4448b76ac95868ca33f527383d20/roles/openshift_health_checker/openshift_checks/mixins.py#L28-L30 could be similarly modified.