Buildout on vagrant requires explicit cfg

[fulv]

If you run bin/buildout on vagrant without specifying -c vagrant.cfg, you will end up with a broken site, because filestorage and blobstorage paths point to the buildout dir, instead of /home/vagrant. @pbauer My question is: how have you handled this during training? Did you remind people that if they use vagrant, every time they see bin/buildout, they must actually use `bin/buildout -c vagrant.cfg?