labs: skip osbash scripts in Vagrant

Make Vagrant skip not only osbash commands (lines starting with "cmd "),
but also scripts in the osbash directory. This allows us to use the same
config/scripts.* files for osbash and Vagrant while preventing Vagrant
from executing scripts that are only meant for osbash.

Change-Id: I86d1bb6065a58edcc67015603da59af9d6aff4c7
Implements: blueprint openstack-training-labs
Merge "labs: skip osbash scripts in Vagrant"