This way the vagrant user can access the docker daemon socket.

Closes-Bug: #1482381
Change-Id: Ic631a94c5b9665b9ec39be5c0454e4c1fa6a33b1

With Vagrant it becomes real easy to create a dev environment to
test and checkout $code. The focus is specifically on setting up
an environment to play around in, developing Kolla and showing
what it is capable of in a clean virtualised environment. When
done, the environment can be destroy and re-created at will when
needed.

Change-Id: I440d004e76c337f298cad2397cf4c13f2cc35ddb
Implements: blueprint vagrant-devenv