Issues #1691 Entry for VMWare's vagrant provisioning is breaking Vagrant...

Issues #1691 Entry for VMWare's vagrant provisioning is breaking Vagrant usage. "disabled is a symbol and requires a colon"

I was attempting to run the following introduction guide http://docs.docker.io/en/latest/installation/vagrant/ and ran into the following issue https://github.com/dotcloud/docker/issues/1691. It has a listed fix and is closed but change was not added into the code base.

This is a small change to correct this issue.