Fix ansible.provisioning_path
Fix ansible.provisioning_path

This fixes the following error:

    ==> default: Running provisioner: ansible_local...
    `playbook` does not exist on the guest: /home/vagrant/digital_slide_archive/ansible/vagrant-playbook.yml

ImageMarkup/isic-archive,ImageMarkup/isic-archive,ImageMarkup/isic-archive,ImageMarkup/isic-archive