* Use unix:// prefix for CSI_ENDPOINT variable by default
* Some plugins have strict validation over the format of the
`CSI_ENDPOINT` variable, and unfortunately not all plugins
agree. Allow the user to override the `CSI_ENDPOINT` to workaround
those cases.
* Update all demos and tests with CSI_ENDPOINT
This changeset expands on the existing demonstration we had for Ceph by
showing volume creation. It includes a demo setup for Ceph on Vagrant so that
you don't need a whole Ceph cluster to try it out.
