download: get ansible playbooks

Ansible playbooks are used to manage the orchestration of the upgrade
process.
This patch allow to download them on the install-server, then the
"upgrade" jenkins job will be allow to run the Ansible playbooks.

Signed-off-by: Emilien Macchi <emilien.macchi@enovance.com>
Merge pull request #7 from enovance/ansible

download: get ansible playbooks