Centos images will build on ubuntu only with docker+devicemapper (NOT AUFS !)

BIT OF BACKSTORY:

I initially reported this bug https://bugs.launchpad.net/kolla/+bug/1473233 almost a week ago, when trying to build all centos binary images on fresh ubuntu 14 environemtn but they kept failing with error related to ""install systemd rpm"" .
A little of research helped me figured out its a bug related to docker+aufs where docker defaults to aufs in ubuntu.
Here is the upstream docker bug : https://github.com/docker/docker/issues/6980

MORE INFO EXPLAINED:

as mentioned earlier, due to docker bug #6980 , centos images would only build on docker+devicemapper. When it came known, i decided to switch my docker daemon on Ubuntu to use devicemapper , which i thought would be as simple as :

docker -d -s devicemapper &

but no .. it instantly failed with error "driver not supported" . I looked up and it was easy enough to see there is another docker bug here https://github.com/docker/docker/issues/14035 .

what this means is you cant just start a "static binary" of docker like the one you get from get.docker.com and start it with `-s devicemapper` on ubuntu. No it wont work !!!

in the bug https://github.com/docker/docker/issues/14035, docker folks suggest using Docker dynamic binary for devicemapper because libdevmapper isnt linked to Udev ( see https://github.com/docker/docker/issues/14035#issuecomment-113469709 ) instead of manually downloading like kolla docs suggest to get from get.docker.com . The complete step by step guide i have created of github gist here
https://gist.github.com/hayderimran7/e65c107569df52016297

SOLUTIONS NEEDED:
- First, explicitly mention in docs when to download static docker binary, in the case of non-ubuntu OS, it should be suggested to get static binnary, or building non-centos binaries on ubuntu systems.

but when using ubuntu for building centos/rdo images, then path of docker+devicemapper where docker is a dynamic binary built locally , should be suggested to users.\

- Add detection logic, if system is ubuntu, and from `docker info` the storage is aufs, it should exit right away without going to build images and showing systemd error.

ADDITIONAL WORK APPRECIATED:
it would be really nice, for folks on ubuntu systems, that just download the latest centos rdo images from kollaglue docker hub,. unfortuantely those are outdated images with several bugs.

if we have some kind of gating job to update these docker hub images frequently, that would be great and appreciated. =)

thanks