properly check if docker is usable for $USER

[Harm Weites]

Introduce a proper check on usability of docker and bail if it's not usable. The current behavior is to 'just read the docs!', which not everybody does, and inflict mayhem if $USER tries to do anything docker. Not good.

[Jeff Peeler (jpeeler-z)]

Yes, don't just do a group membership test. Perhaps checking the return value of "docker info" may work, but in the case of the docker client not being installed (such as inside an atomic container), checking the permissions of the socket file in the default location I would think is the best approach.

[Swapnil Kulkarni (coolsvap-deactivatedaccount)]

Even if I check the permission on /var/run/docker.sock, it does not solve the problem. The group ownership can be checked by any user and it does not validate if the user can execute the docker commands.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/201022

[Swapnil Kulkarni (coolsvap-deactivatedaccount)]

I checked docker ps in atomic host as well and it works so I believe we can use it to validate the user. docker info works for user without docker privileges

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/201022
Committed: https://git.openstack.org/cgit/stackforge/kolla/commit/?id=1f0acbd0cd47c4872fd57189181e06dc2bd7891b
Submitter: Jenkins
Branch: master

commit 1f0acbd0cd47c4872fd57189181e06dc2bd7891b
Author: Swapnil Kulkarni <email address hidden>
Date: Mon Jul 13 07:11:27 2015 +0000

    Update scripts to check if docker is usable for $USER

    Added new script for checking user permissions on
    docker command execution

    Change-Id: I3b727590d9a29f416f5b847912b7250c555c2333
    Closes-Bug: #1473554