Add a new option, `use_sftp` to the ansible provisioner. It's default
value is false; ansible provisioner will use SCP by default.
Refactor to consistently set all configure options for ansible
provisioner in the Prepare step.
Remove incorrect information about `ANSIBLE_HOST_KEY_CHECKING=False`
being set when `ansible_env_vars` is not set in the packer template.
Update BATS tests for the ansible provisioner to actually check that the
fetched directory contains the contents expected. This revealed a
problem with the all_options template that required adding a host to the
hosts list in the test playbook.
f760ab2fd8